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  Subjects -> COMPUTER SCIENCE (Total: 1993 journals)
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COMPUTER SCIENCE (1157 journals)                  1 2 3 4 5 6 | Last

Showing 1 - 200 of 872 Journals sorted alphabetically
3D Printing and Additive Manufacturing     Full-text available via subscription   (Followers: 13)
Abakós     Open Access   (Followers: 3)
Academy of Information and Management Sciences Journal     Full-text available via subscription   (Followers: 69)
ACM Computing Surveys     Hybrid Journal   (Followers: 22)
ACM Journal on Computing and Cultural Heritage     Hybrid Journal   (Followers: 9)
ACM Journal on Emerging Technologies in Computing Systems     Hybrid Journal   (Followers: 13)
ACM Transactions on Accessible Computing (TACCESS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 16)
ACM Transactions on Applied Perception (TAP)     Hybrid Journal   (Followers: 6)
ACM Transactions on Architecture and Code Optimization (TACO)     Hybrid Journal   (Followers: 9)
ACM Transactions on Autonomous and Adaptive Systems (TAAS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Computation Theory (TOCT)     Hybrid Journal   (Followers: 11)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 4)
ACM Transactions on Computer Systems (TOCS)     Hybrid Journal   (Followers: 18)
ACM Transactions on Computer-Human Interaction     Hybrid Journal   (Followers: 13)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 3)
ACM Transactions on Design Automation of Electronic Systems (TODAES)     Hybrid Journal   (Followers: 1)
ACM Transactions on Economics and Computation     Hybrid Journal  
ACM Transactions on Embedded Computing Systems (TECS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Information Systems (TOIS)     Hybrid Journal   (Followers: 20)
ACM Transactions on Intelligent Systems and Technology (TIST)     Hybrid Journal   (Followers: 8)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)     Hybrid Journal   (Followers: 10)
ACM Transactions on Reconfigurable Technology and Systems (TRETS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Sensor Networks (TOSN)     Hybrid Journal   (Followers: 8)
ACM Transactions on Speech and Language Processing (TSLP)     Hybrid Journal   (Followers: 11)
ACM Transactions on Storage     Hybrid Journal  
ACS Applied Materials & Interfaces     Full-text available via subscription   (Followers: 21)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Ad Hoc Networks     Hybrid Journal   (Followers: 11)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Advanced Engineering Materials     Hybrid Journal   (Followers: 26)
Advanced Science Letters     Full-text available via subscription   (Followers: 7)
Advances in Adaptive Data Analysis     Hybrid Journal   (Followers: 8)
Advances in Artificial Intelligence     Open Access   (Followers: 16)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 15)
Advances in Computer Science : an International Journal     Open Access   (Followers: 13)
Advances in Computing     Open Access   (Followers: 2)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 53)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 10)
Advances in Human-Computer Interaction     Open Access   (Followers: 20)
Advances in Materials Sciences     Open Access   (Followers: 16)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 37)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access   (Followers: 1)
AEU - International Journal of Electronics and Communications     Hybrid Journal   (Followers: 8)
African Journal of Information and Communication     Open Access   (Followers: 6)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Air, Soil & Water Research     Open Access   (Followers: 7)
AIS Transactions on Human-Computer Interaction     Open Access   (Followers: 6)
Algebras and Representation Theory     Hybrid Journal   (Followers: 1)
Algorithms     Open Access   (Followers: 11)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 4)
American Journal of Computational Mathematics     Open Access   (Followers: 4)
American Journal of Information Systems     Open Access   (Followers: 7)
American Journal of Sensor Technology     Open Access   (Followers: 4)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2)
Analog Integrated Circuits and Signal Processing     Hybrid Journal   (Followers: 7)
Analysis in Theory and Applications     Hybrid Journal   (Followers: 1)
Animation Practice, Process & Production     Hybrid Journal   (Followers: 5)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Data Science     Hybrid Journal   (Followers: 9)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 6)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Software Engineering     Hybrid Journal   (Followers: 12)
Annual Reviews in Control     Hybrid Journal   (Followers: 6)
Anuario Americanista Europeo     Open Access  
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applied and Computational Harmonic Analysis     Full-text available via subscription   (Followers: 2)
Applied Artificial Intelligence: An International Journal     Hybrid Journal   (Followers: 14)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Clinical Informatics     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Computer Systems     Open Access   (Followers: 1)
Applied Informatics     Open Access  
Applied Mathematics and Computation     Hybrid Journal   (Followers: 32)
Applied Medical Informatics     Open Access   (Followers: 10)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Soft Computing     Hybrid Journal   (Followers: 16)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Architectural Theory Review     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 5)
Archive of Numerical Software     Open Access  
Archives and Museum Informatics     Hybrid Journal   (Followers: 125)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Artifact     Hybrid Journal   (Followers: 2)
Artificial Life     Hybrid Journal   (Followers: 6)
Asia Pacific Journal on Computational Engineering     Open Access  
Asia-Pacific Journal of Information Technology and Multimedia     Open Access   (Followers: 1)
Asian Journal of Computer Science and Information Technology     Open Access  
Asian Journal of Control     Hybrid Journal  
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
Australian Educational Computing     Open Access  
Automatic Control and Computer Sciences     Hybrid Journal   (Followers: 3)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Automatica     Hybrid Journal   (Followers: 9)
Automation in Construction     Hybrid Journal   (Followers: 6)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 8)
Basin Research     Hybrid Journal   (Followers: 5)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Bioinformatics     Hybrid Journal   (Followers: 308)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 31)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 46)
British Journal of Educational Technology     Hybrid Journal   (Followers: 123)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
c't Magazin fuer Computertechnik     Full-text available via subscription   (Followers: 2)
CALCOLO     Hybrid Journal  
Calphad     Hybrid Journal  
Canadian Journal of Electrical and Computer Engineering     Full-text available via subscription   (Followers: 14)
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal  
Cell Communication and Signaling     Open Access   (Followers: 1)
Central European Journal of Computer Science     Hybrid Journal   (Followers: 5)
CERN IdeaSquare Journal of Experimental Innovation     Open Access  
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 7)
China Communications     Full-text available via subscription   (Followers: 7)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
CIN Computers Informatics Nursing     Full-text available via subscription   (Followers: 12)
Circuits and Systems     Open Access   (Followers: 16)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
CLEI Electronic Journal     Open Access  
Clin-Alert     Hybrid Journal   (Followers: 1)
Cluster Computing     Hybrid Journal   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 4)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Communication Methods and Measures     Hybrid Journal   (Followers: 11)
Communication Theory     Hybrid Journal   (Followers: 20)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Algebra     Hybrid Journal   (Followers: 3)
Communications in Partial Differential Equations     Hybrid Journal   (Followers: 3)
Communications of the ACM     Full-text available via subscription   (Followers: 53)
Communications of the Association for Information Systems     Open Access   (Followers: 18)
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering     Hybrid Journal   (Followers: 3)
Complex & Intelligent Systems     Open Access  
Complex Adaptive Systems Modeling     Open Access  
Complex Analysis and Operator Theory     Hybrid Journal   (Followers: 2)
Complexity     Hybrid Journal   (Followers: 6)
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 9)
Computación y Sistemas     Open Access  
Computation     Open Access  
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Astrophysics and Cosmology     Open Access   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computational Cognitive Science     Open Access   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Condensed Matter     Open Access  
Computational Ecology and Software     Open Access   (Followers: 9)
Computational Economics     Hybrid Journal   (Followers: 9)
Computational Geosciences     Hybrid Journal   (Followers: 14)
Computational Linguistics     Open Access   (Followers: 23)
Computational Management Science     Hybrid Journal  
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 4)
Computational Methods and Function Theory     Hybrid Journal  
Computational Molecular Bioscience     Open Access   (Followers: 2)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Particle Mechanics     Hybrid Journal   (Followers: 1)
Computational Research     Open Access   (Followers: 1)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computational Science and Techniques     Open Access  
Computational Statistics     Hybrid Journal   (Followers: 13)
Computational Statistics & Data Analysis     Hybrid Journal   (Followers: 31)
Computer     Full-text available via subscription   (Followers: 84)
Computer Aided Surgery     Hybrid Journal   (Followers: 3)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computer Communications     Hybrid Journal   (Followers: 10)
Computer Engineering and Applications Journal     Open Access   (Followers: 5)
Computer Journal     Hybrid Journal   (Followers: 7)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 22)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 10)
Computer Methods in the Geosciences     Full-text available via subscription   (Followers: 1)
Computer Music Journal     Hybrid Journal   (Followers: 16)
Computer Physics Communications     Hybrid Journal   (Followers: 6)
Computer Science - Research and Development     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 17)
Computer Science and Information Technology     Open Access   (Followers: 11)
Computer Science Education     Hybrid Journal   (Followers: 12)
Computer Science Journal     Open Access   (Followers: 20)
Computer Science Master Research     Open Access   (Followers: 10)
Computer Science Review     Hybrid Journal   (Followers: 10)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Engineering Materials
  [SJR: 0.81]   [H-I: 81]   [26 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1438-1656 - ISSN (Online) 1527-2648
   Published by John Wiley and Sons Homepage  [1577 journals]
  • Effect of Thermal Oxidation on Microstructure and Corrosion Behavior of
           the PVD Hf-Coated Mg Alloy
    • Authors: Dongfang Zhang; Zhengbing Qi, Binbin Wei, Zhoucheng Wang
      Abstract: Hafnium coatings are fabricated on magnesium alloys by magnetron sputtering and are further submitted to the thermal oxidation treatment at temperature of 200, 300, and 400 °C. The thin hafnium oxide film and new grain boundaries are observed on the hafnium coatings during the appropriate treatment temperature (300 °C). These changes in microstructure result in surface densification, oxidation, and low porosity of the treated coating that significantly decrease its susceptibility to corrosion. Consequently, the thermal oxidation treatment hafnium coating exhibits a more positive corrosion potential, lower corrosion current density, and higher polarization resistance than that of the as-deposited coating using an electrochemical system. Moreover, the enhanced adhesion of the treated coating produced by applying an appropriate treatment temperature facilitates an efficient long-term protection of magnesium alloy.Thermal oxidation as an effective yet feasible post-treatment is conducting on the PVD Hf coated Mg alloy. Surface densification, thin oxide film, and enhanced adhesion are obtained on the post treated coating. As a result, the treated coating exhibits more efficient barrier to corrosive media with positive corrosion potential, low corrosion current density, and high polarization resistance.
      PubDate: 2017-09-18T01:00:38.093829-05:
      DOI: 10.1002/adem.201700556
       
  • MWCNTs as Conductive Network for Monodispersed Fe3O4 Nanoparticles to
           Enhance the Wave Absorption Performances
    • Authors: Kaili Yu; Min Zeng, Yichao Yin, Xiaojun Zeng, Jue Liu, Ya Li, Wukui Tang, Yu Wang, Jing An, Jun He, Ronghai Yu
      Abstract: Magnetic oxides are widely used as electromagnetic (EM) wave absorbers. To promote the absorption efficiency, tremendous efforts have been contributed to adjusting the composite, structure, and size of magnetic loss materials. Employing carbon materials (CNTs, CF, graphene, PANI) is an efficient way to improve the dielectric loss of the matrix. Anchoring the tiny-monodispersed Fe3O4 nanoparticles (NPs) onto the lightweight multi − walled carbon nanotubes (MWCNTs) leads to improve dielectric loss and impedance matching characteristic. Magnetic Fe3O4 NPs along the one-dimensional nanotubes direction play a good synergetic role with MWCNTs due to the interfacial strong chemical and structure bonding. The as-synthesized Fe3O4/MWCNTs nanocomposites exhibit efficient EM wave absorption characteristics (RL av−10 dB) with a maximum reflection loss of −63.64 dB at 12.08 GHz and a diminutive thickness of only 1.6 mm. The magnetic Fe3O4 NPs show strong chemical and structure bonding with the one-dimensional MWCNTs. This work may show a way to broaden the application of such kinds of lightweight high-performance absorbing materials frameworks.Anchoring the tiny and monodispersed Fe3O4 NPs onto the lightweight MWCNTs results in a strong bonding in Fe3O4/MWCNTs nanocomposites, which exhibit excellent EM wave absorption properties. The MWCNTs can act as the conductive network to enhance the dielectric loss and balance the magnetic loss for good impedance matching.
      PubDate: 2017-09-18T01:00:29.878778-05:
      DOI: 10.1002/adem.201700543
       
  • Graphene Oxide/Polymer-Based Biomaterials
    • Authors: Duygu Ege; Ali Reza Kamali, Aldo R. Boccaccini
      Abstract: Since its discovery in 2004, derivatives of graphene have been developed and heavily investigated in the field of tissue engineering. Among the most extensively studied forms of graphene, graphene oxide (GO), and GO/polymer-based nanocomposites have attracted great attention in various forms such as films, 3D porous scaffolds, electrospun mats, hydrogels, and nacre-like structures. In this review, the most actively investigated GO/polymer nanocomposites are presented and discussed, these nanocomposites are based on chitosan, cellulose, starch, alginate, gellan gum, poly(vinyl alcohol) (PVA), poly(acrylamide), poly(ϵ-caprolactone) (PCL), poly(lactic acid) (PLLA), poly(lactide-co-glycolide) (PLGA), gelatin, collagen, and silk fibroin (SF). The biological and mechanical performance of such nanocomposites are comprehensively scrutinized and ongoing research questions are addressed. The analysis of the literature reveals overall the great potential of GO/polymer nanocomposites in tissue engineering strategies and indicates also a series of challenges requiring further research efforts.In this review paper, the mechanical and biological performance of graphene oxide/polymeric nanocomposites are analyzed in detail and discussed. Additionally, useful graphics are provided which lead researchers to compare the mechanical properties of films, electrospun mats, fibers, nacre-like structures, and hydrogels of graphene oxide/polymeric nanocomposites at first glance. Finally, the potential of these nanocomposites in tissue engineering are reported with suggestions for future research.
      PubDate: 2017-09-14T07:41:13.801311-05:
      DOI: 10.1002/adem.201700627
       
  • Hydrogen Trapping in Some Automotive Martensitic Advanced High-Strength
           Steels
    • Authors: Jeffrey Venezuela; Qingjun Zhou, Qinglong Liu, Mingxing Zhang, Andrej Atrens
      Abstract: Hydrogen permeation experiments are used to investigate hydrogen trapping in commercial automotive martensitic advanced high-strength steels. Hydrogen trapping increases with increasing mechanical strength, as indicated by (i) the decrease in the hydrogen diffusion coefficient, and (ii) the increase in reversible hydrogen trap density. The measured trap densities are in the order of ≈1017– ≈ 1018 cm−3. The relationship between trapping characteristics and HE susceptibility of MS-AHSS is discussed in terms of Hydrogen Enhanced Macroscopic Plasticity (HEMP) and Hydrogen Assisted Micro-fracture (HAM).Reversible trapping of hydrogen by dislocations may explain the hydrogen-influenced behavior in the MS-AHSS: (i) the reduction of the yield strength by the Hydrogen Enhanced Macroscopic Plasticity (HELP) mechanism, and (ii) the occurrence of shear micro-fracture by the Hydrogen Assisted Micro-fracture (HAM) mechanism.
      PubDate: 2017-09-13T13:02:10.393178-05:
      DOI: 10.1002/adem.201700468
       
  • Fused Deposition Modeling for Unmanned Aerial Vehicles (UAVs): A Review
    • Authors: Helge Klippstein; Alejandro Diaz De Cerio Sanchez, Hany Hassanin, Yahya Zweiri, Lakmal Seneviratne
      Abstract: Additive Manufacturing (AM) is a game changing production technology for aerospace applications. Fused deposition modeling is one of the most widely used AM technologies and recently has gained much attention in the advancement of many products. This paper introduces an extensive review of fused deposition modeling and its application in the development of high performance unmanned aerial vehicles. The process methodology, materials, post processing, and properties of its products are discussed in details. Successful examples of using this technology for making functional, lightweight, and high endurance unmanned aerial vehicles are also highlighted. In addition, major opportunities, limitations, and outlook of fused deposition modeling are also explored. The paper shows that the emerge of fused deposition modeling as a robust technique for unmanned aerial vehicles represents a good opportunity to produce compact, strong, lightweight structures, and functional parts with embedded electronic.Fused deposition modeling (FDM) and Unmanned Ariel vehicles (UAVs), are fast growing technologies, have attracted a great deal of attention. This review studies the process methodology challenges, opportunities, and outlook of FDM and its application in the development of high performance UAVs.
      PubDate: 2017-09-12T02:21:35.040109-05:
      DOI: 10.1002/adem.201700552
       
  • Threshold Fluence Measurement for Laser Liftoof InP Thin Films by
           Selective Absorption
    • Authors: Antony Jan; Benjamin A. Reeves, Yoeri van de Burgt, Garrett J. Hayes, Bruce M. Clemens
      Abstract: We explore conditions for achieving laser liftoff in epitaxially grown heterojunctions, in which single crystal thin films can be separated from their growth substrates using a selectively absorbing buried intermediate layer. Because this highly non-linear process is subject to a variety of process instabilities, it is essential to accurately characterize the parameters resulting in liftoff. Here, we present an InP/InGaAs/InP heterojunction as a model system for such characterization. We show separation of InP thin films from single crystal InP growth substrates, wherein a ≈10 ns, Nd:YAG laser pulse selectively heats a coherently strained, buried InGaAs layer. We develop a technique to measure liftoff threshold fluences within an inhomogeneous laser spatial profile, and apply this technique to determine threshold fluences of the order 0.5 J cm−2 for our specimens. We find that the fluence at the InGaAs layer is limited by non-linear absorption and InP surface damage at high powers, and measure the energy transmission in an InP substrate from 0 to 8 J cm−2. Characterization of the ejected thin films shows crack-free, single crystal InP. Finally, we present evidence that the hot InGaAs initiates a liquid phase front that travels into the InP substrate during liftoff.In epitaxial laser liftoff, the selective absorption of a bright laser pulse by a buried layer results in the separation of the thin film above it from the substrate below, as shown in the accompanying figure. The wafer can be washed and reused for growth, lowering device costs. The resulting films are single crystal and crack free.
      PubDate: 2017-09-11T10:26:16.695208-05:
      DOI: 10.1002/adem.201700624
       
  • Grain Refinement through Shear Banding in Severely Plastic Deformed A206
           Aluminum Alloy
    • Authors: Parya Teymoory; Abbas Zarei-Hanzaki, Ehsan Farabi, Hossein Monajati, Hamid Reza Abedi
      Abstract: The present work is conducted to study the microstructure and texture evolutions in an as-cast A206 aluminum alloy after applying severe plastic deformation. Toward this end, the material is severely deformed through accumulative back extrusion (ABE) technique at 200 °C and followed by assessing the room temperature mechanical properties of the products. The macro shear-bands formation in the highly strained regions can result in grain refinement through the geometric dynamic recrystallization mechanism. A significant refinement is also characterized within the micro shear-bands; this is attributed to the intensified substructure development and the occurrence of continuous dynamic recrystallization. The corresponding inverse pole figure maps show similar orientation for these newly refined grains with the parent ones. A random texture is produced through sub-grain rotation to dissimilar orientation at the intersection of micro-bands. The assessment of mechanical properties of the processed materials reveal significant increase in both yield and ultimate tensile strength values. The hardness profiles also demonstrate a relatively homogenous microstructure after three and five ABE passes holding a mean hardness value of 183 Vickers.A206 alloy is severely deformed by accumulative back extrusion (ABE) technique at 200 °C and then the room temperature mechanical properties of the products are scrutinized. Enhancement of these properties is attributed to grain refinement that is caused by the presence of micro and macro-shear bands in the heavily deformed regions of the material.
      PubDate: 2017-09-11T01:46:20.782144-05:
      DOI: 10.1002/adem.201700502
       
  • Hot Deformation Behavior, Dynamic Recrystallization, and Texture Evolution
           of Ti–22Al–25Nb Alloy
    • Authors: Yang Wu; Hongchao Kou, Bin Tang, Jinshan Li
      Abstract: The hot deformation behavior, dynamic recrystallization, and texture evolution of Ti–22Al–25Nb alloy in the temperature range of 950–1050 °C and strain rate range of 0.001–1 s−1 is investigated by plane-strain compression testing on the Gleeble-3500 thermo-mechanical simulator. The results show that the flow stress decreases with the increase of temperature and decrease of strain rate. Besides, the flow curves appear a serrate oscillation at a strain rate of 0.1 s−1 for all the temperature ranges, which may result from instability such as flow localization or micro-cracking. The flow behavior can be expressed by the conventional hyperbolic sine constitutive equation and the calculated deformation activation energy Q in the (α2 + B2) and B2 regions are 631.367 and 304.812 kJ mol−1, respectively. The microstructure evolution is strongly dependent on the deformation parameters, and dynamic recrystallization (DRX) is the dominant softening mechanism in the (α2 + B2) region, including discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX). In addition, the ηbcc-fiber of {110} is the dominant texture component in deformed Ti–22Al–25Nb alloy. It is observed that the weakening of the deformation texture is accompanied by the occurrence of DRX, which can be attributed to the large misorientation between DRX grains and neighboring B2 matrix induced by the rotation of DRX grains toward the preferred slip systems.During the process of compression deformation, dynamic recrystallization (DRX) is the dominant softening mechanism in Ti–22Al–25Nb alloy, including discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX). In addition, the ηbcc-fiber of {110} is the dominate texture component and the weakening of the deformation texture is accompanied by the occurrence of DRX.
      PubDate: 2017-09-11T01:45:53.110381-05:
      DOI: 10.1002/adem.201700587
       
  • Influence of Stress-Aging Processing on Precipitates and Mechanical
           Properties of a 7075 Aluminum Alloy
    • Authors: Y. C. Lin; Yu-Qiang Jiang, Jin-Long Zhang, Xiao-Min Chen
      Abstract: Two-step stress-aging tests, as well as pre-treatment plus stress-aging experiments, are performed on a 7075 aluminum (Al–Zn–Mg–Cu) alloy. Influences of stress-aging parameters on mechanical behavior and fracture mechanism are investigated through uniaxial tensile test and fracture morphology analysis. It is revealed that the stress-aging dramatically influences the mechanical properties and fracture characteristics of the studied alloy, which is contributed to the sensitivity of microstructures to stress-aging. When the alloy undergoes two-step stress-aging, the ultimate tensile strength and yield strength first increase and then decrease with the increased first step stress-aging temperature, while the elongation first decreases and then increases. For the retrogression pre-treated plus stress-aged alloy, the yield strength first increases and then drops with the increased retrogression pre-treatment time, while the ultimate tensile strength almost remains stable. Furthermore, the elongation continuously increases with the increased retrogression pre-treatment time. The observation of fracture morphology indicates that the dimple-type intergranular fracture is the main fracture mechanism for the two-step stress-aged and retrogression pre-treated plus stress-aged alloys.Effects of stress-aging on mechanical behavior and fracture mechanisms of an Al–Zn–Mg–Cu alloy are investigated. It is found that the mechanical strengths of the two-step stress-aged alloy first increase and then decrease with the increased first step stress-aging temperature, while the elongation first decreases and then increases. The dimple-type intergranular fracture is the main fracture mechanism for stress-aged alloys.
      PubDate: 2017-09-07T08:00:52.278529-05:
      DOI: 10.1002/adem.201700583
       
  • Equivalent Hydrogen Fugacity during Electrochemical Charging of 980DP
           Steel Determined by Thermal Desorption Spectroscopy
    • Authors: Qinglong Liu; Evan Gray, Jeffrey Venezuela, Qingjun Zhou, Clotario Tapia-Bastidas, Mingxing Zhang, Andrej Atrens
      Abstract: Thermal desorption spectroscopy (TDS) is used to analyze hydrogen in 980DP after (i) electrochemical charging, and (ii) gaseous charging. The hydrogen concentration increases with (i) a more negative charging potential and (ii) an increasing hydrogen gas pressure. For charging in 0.1 M NaOH, the hydrogen fugacity for 980DP is similar to that for (i) low interstitial steel, and (ii) MS1500, and is greater than that for the 3.5NiCrMoV steel. This indicates an influence of steel chemistry on the hydrogen evolution reaction. The de-trapping activation energies are 40.5 and 50.2 kJ mol−1, indicating hydrogen traps at boundary defects.The figure shows that, for cathodic hydrogen charging in 0.1 M NaOH, the hydrogen fugacity is similar for the (i) 980DP steel (ii) low interstitial steel, and (iii) MS1500, and was greater than the fugacity for the 3.5NiCrMoV steel. This indicates an influence of steel chemistry, most likely, on the details of the hydrogen evolution reaction.
      PubDate: 2017-09-07T07:41:18.465735-05:
      DOI: 10.1002/adem.201700469
       
  • A Combined Analytic, Numeric, and Experimental Investigation Performed on
           NiTi/NiTiCu Bi-Layer Composites under Tensile Loading
    • Authors: Milad Taghizadeh; Mahmoud Nili-Ahmadabadi, Mostafa Baghani, Mohammad Hassan Malekoshoaraei
      Abstract: Adjusting mechanical behavior and controlling deformation parameters are significant tasks in designing shape memory components. In this paper, an analytical model describes the deformation behavior of NiTi/NiTiCu bi-layer composites under tensile loading. Different deformation stages are considered based on single mechanical behavior at each stage. Closed-form equations are derived for stress–strain variations of bi-layer composites under uniaxial loading–unloading. Bi-layer composites made via the diffusion bonding method from single layers of NiTi alloy with a composition of Ti-50.7 at.% Ni, as an austenitic layer, and Ti-45 at% Ni-5 at% Cu, as a martensitic layer, are produced by the vacuum arc remelting technique. The tensile behavior of single- and bi-layers is investigated by using loading–unloading experiments to find the nominal stress–strain curves. Numerical simulations are also done by employing Lagoudas constitutive model to simulate stress–strain diagrams. The solutions of the analytical method presented are validated by using the numerical simulations as well as the experimental results. With regard to the results obtained from the analytical modeling, the numerical simulations, and the experiments, it is evident that the bi-layer composites with different thickness ratios provide adjustable mechanical behavior that can be considered in different application designs, for example, actuators equipped with shape memory components.In this paper, an analytical model describes the deformation behavior of NiTi/NiTiCu bi-layer composites under tensile loading. Bi-layer composites are made via diffusion bonding method and their tensile behavior is investigated by using loading-unloading experiments. Numerical simulations are also done by employing Lagoudas constitutive model. The model shows a good agreement with both the experimental and FEM results.
      PubDate: 2017-09-06T23:59:47.460143-05:
      DOI: 10.1002/adem.201700395
       
  • Measurement of Texture Gradient in Heavily Cold-Drawn Pearlitic Wires
    • Authors: Aurélie Jamoneau; Jean-Hubert Schmitt, Denis Solas
      Abstract: It is well established that cold-drawing of pearlitic wire develops a strong anisotropy due to a preferential orientation of the ferrite phase parallel to the wire axis. The subsequent wire behavior during torsion, which mainly occurs during assembling of drawn wires, is correlated with the texture and its gradient along the wire radius. Although different attempts were made in the past to measure the texture after drawing, it is still challenging since the final wire diameter is on the order of 0.3 mm. The paper presents a simple and robust method to measure the texture gradient by X-ray diffraction. First, to overcome the problems of a composite sample made of parallel wires, an isotropic reference sample is prepared by cycles of austenite transformation and quenching. The texture gradient is measured at different thicknesses by dissolving the external surface of the wires. This allows the investigation of the first 40 μm of depth. Finally, the results are compared with EBSD measurements on a longitudinal cross-section to quantify the influence of the drawing conditions: A flat schedule with constant die angles favors a fiber texture with a weak gradient, while increasing the drawing angle for three dies increases the gradient.An isotropic pearlitic wire is used as a reference with which to correct pole figures obtained by X-ray diffraction on drawn wire surface (R). The textural evolution is measured along the radius via successive surface dissolutions (0.87R and 0.73R). Results are compared to EBSD maps at equivalent depths to quantify the effects of drawing conditions.
      PubDate: 2017-09-06T11:08:21.943881-05:
      DOI: 10.1002/adem.201700279
       
  • Mechanical Properties, Fatigue Life, and Electrical Conductivity of
           Cu–Cr–Hf Alloy after Equal Channel Angular Pressing
    • Authors: Daria V. Shangina; Vladimir F. Terent'ev, Dmitry V. Prosvirnin, Olga V. Antonova, Natalia R. Bochvar, Mikhail V. Gorshenkov, Georgy I. Raab, Sergey V. Dobatkin
      Abstract: Structure, mechanical, and service properties of a Cu–Cr–Hf alloy after quenching, equal-channel angular pressing (ECAP), and subsequent aging have been studied. The positive effects of ultrafine-grained structure formation (grain/subgrain size of ≈200 nm) during ECAP and strengthening particles precipitation upon subsequent aging at 450 °C on the mechanical and fatigue properties of the alloy are shown. Ultrafine-grained Cu–Cr–Hf alloy after aging shows increasing in the fatigue limit on the basis of 107 cycles from 185 to 375 MPa relative to that of the initial coarse-grained state. The alloy after ECAP and aging also exhibits sufficient elongation to failure (11.4%) and good electrical conductivity (78%IACS).Mechanical and service properties of a Cu–Cr–Hf alloy after equal channel angular pressing (ECAP) and aging have been studied. The positive effects of ultrafine-grained structure and precipitates on the tensile and fatigue properties of the material are shown. The alloy after ECAP and aging exhibits sufficient elongation and good electrical conductivity.
      PubDate: 2017-09-05T07:06:54.713546-05:
      DOI: 10.1002/adem.201700536
       
  • Uniting Strength and Toughness of Al Matrix Composites with Coordinated
           Al3Ni and Al3Ti Reinforcements
    • Authors: Frederick M. Heim; Yunya Zhang, Xiaodong Li
      Abstract: Hybrid aluminum composites are fabricated in a novel manner to characteristically induce a layer-wise aligned distribution of micro-scale Al3Ni and Al3Ti intermetallic particles that are formed in situ within a ductile Al matrix. The simple and unique Rolling of Randomly Orientated Layer-wise Materials (RROLM) manufacturing methodology enables microstructural tailoring of the intermetallic reinforcing particles to prescribe enhanced crack tip deflection caused by the complex interaction of local veins of reinforcement particles, in an effort to overshadow the classical loss of toughness in large-particle reinforced composites. The complimentary reinforcements and their interface with the Al matrix are revealed to have a gradual transition zone that functions to maintain critical cohesion with the particles and the matrix, empowering the superior load transfer capability of the particles, and reducing microvoid penetration into the matrix. In situ three-point bending observations combined with a local strain field analysis, demonstrate the distinctive crack deflection mechanisms exhibit by the composite. Deviating from the norm, this specialized particle reinforced composite exhibited both strengthening and toughening mechanisms simultaneously, over control samples. The investigated design strategy and model material will assist materials development toward light-weight, stronger, and tougher particle reinforced Al matrix composites.Specialized aluminum matrix composites microstructurally tailored with coordinated dual intermetallic reinforcement particles have been developed though a simple, yet original, methodology, which is specifically designed to enhance toughness and strength simultaneously. Bi-level microcracking and crack tip deflection are expected to have enabled the improved toughness. Hybrid materials like these are anticipated to enable future designs.
      PubDate: 2017-09-05T07:06:25.40406-05:0
      DOI: 10.1002/adem.201700605
       
  • Current Status and Recent Developments in Porous Magnesium Fabrication
    • Authors: Alicja Kucharczyk; Krzysztof Naplocha, Jacek W. Kaczmar, Hajo Dieringa, Karl U. Kainer
      Abstract: A significant number of studies have been dedicated to the fabrication and properties of metallic foams. The most recent research is focused on metals with low weight and good mechanical properties, such as titanium, aluminum, and magnesium. Whereas the first two are already fairly well studied and already find application in industry, magnesium currently remains at the research stage. The present review covers the studies conducted on fabrication techniques, surface modifications, and properties of porous structures made of magnesium and its alloys.Magnesium foams attract more and more interest due to their low weight, material availability, and mechanical properties. However, due to the flammability and reactivity of magnesium, not all metallic foam manufacturing methods can be used. Therefore, the article summarizes the latest production methods and modifications of already existing ones as well as information about mechanical properties and corrosion resistance.
      PubDate: 2017-09-05T07:00:47.509733-05:
      DOI: 10.1002/adem.201700562
       
  • Sliding and Migration of Tilt Grain Boundaries in a Mg–Zn–Y
           Alloy
    • Authors: Weiwei Hu; Zhiqing Yang, Hengqiang Ye
      Abstract: Sliding and migration of tilt grain boundaries in a Mg–Zn–Y alloy have been investigated on the atomic scale using aberration-corrected scanning transmission electron microscopy. Grain boundary sliding is accommodated by non-basal dislocations moving along the grain boundary; grain boundary migration is induced by the motion of grain boundary dislocations with synchronized grain boundary diffusion. Simultaneous sliding and migration of tilt boundaries take place in both Mg matrix and long period stacking ordered phases. These results provide evidence for occurrence of grain boundary motion, which may play a role in plasticity of this kind of Mg alloys.Tilt grain boundaries are formed widely as a result of basal slip in Mg alloys. Sliding and migration of tilt grain boundaries take place in both Mg matrix and long period stacking ordered phases in a Mg–Zn–Y alloy. Sliding and migration of tilt grain boundaries accommodated by non-basal dislocations or grain boundary dislocations motion may play important roles in formability of high-strength Mg alloys.
      PubDate: 2017-09-05T07:00:33.282776-05:
      DOI: 10.1002/adem.201700516
       
  • Reticulated Replica Ceramic Foams: Processing, Functionalization, and
           Characterization
    • Authors: Tobias Fey; Ulf Betke, Stefan Rannabauer, Michael Scheffler
      Abstract: Reticulated ceramic foams are used in a wide range of applications such as filters, catalyst supports, lightweight materials, energy absorptions materials, or as scaffolds for tissue engineering as the most common ones. Based on gaseous foaming processes of polymers, a stochastic distribution of closed pores is obtained. By reticulation processing thin foam windows are removed between cells turning a closed cell into an open cell structure. These foams are used as template for porous ceramics manufacturing: With different processing approaches, for example, with dip coating of a ceramic slurry and a subsequent (multistep) thermal treatment ceramic reticulate foams are obtained. A variety of material properties strongly depend on the cell and strut size, as well on material composition. Functionalization of ceramic foam surfaces (outer surface functionalization), for example, with zeolites or nanosized aggregates lead to an increase of the specific surface area or provides catalytic or heat storage functionality. Filling of struts (inner surface functionalization) may lead to improved mechanical stability or may provide functionalities such as electric conductivity. The present work summarizes the processing steps from the template foam to the final cellular ceramic, functionalization strategies, and the most common characterization techniques.This paper reviews reticulated porous ceramics resulting from a manufacturing process described first in 1963. The focus is set to processing parameters, slurry rheology, and porperties to modification strategies and to characterization methods of foam properties. It may help the readers to identify future research potential.
      PubDate: 2017-09-04T05:35:36.763837-05:
      DOI: 10.1002/adem.201700369
       
  • Effects of Multi-Scale Patterning on the Run-In Behavior of
           Steel–Alumina Pairings under Lubricated Conditions
    • Authors: Philipp G. Grützmacher; Andreas Rosenkranz, Adam Szurdak, Carsten Gachot, Gerhard Hirt, Frank Mücklich
      Abstract: In nature, many examples of multi-scale surfaces with outstanding tribological properties such as reduced friction and wear under dry friction and lubricated conditions can be found. To determine whether multi-scale surfaces positively affect the frictional and wear performance, tests are performed on a ball-on-disk tribometer under lubricated conditions using an additive-free poly-alpha-olefine oil under a contact pressure of around 1.29 GPa. For this purpose, stainless steel specimens (AISI 304) are modified by micro-coining (hemispherical structures with a structural depth of either 50 or 95 μm) and subsequently by direct laser interference patterning (cross-like pattern with 9 μm periodicity) to create a multi-scale pattern. The comparison of different sample states (polished reference, laser-patterned, micro-coined, and multi-scale) shows a clear influence of the fabrication technique. In terms of the multi-scale structures, the structural depth of the coarser micro-coining plays an important role. In case of lower coining depths (50 μm), the multi-scale specimens show an increased coefficient of friction compared to the purely micro-coined surfaces, whereas larger coining depths (95 μm) result in stable and lower friction values for the multi-scale patterns.The tribological effects of a multi-scale surface patterning technique are investigated. Steel specimens (AISI 304) are modified by micro-coining and subsequently by direct laser interference patterning to create a multi-scale pattern. Depending on the depth of the coined structures, the multi-scale patterns have positive (deep coined-structures) or negative frictional effects (shallow coined structures).
      PubDate: 2017-09-01T14:36:21.552081-05:
      DOI: 10.1002/adem.201700521
       
  • Electrically Assisted Ultrasonic Nanocrystal Surface Modification of
           Ti6Al4V Alloy
    • Authors: Jun Liu; Sergey Suslov, Shengxi Li, Haifeng Qin, Zhencheng Ren, Gary L. Doll, Hongbo Cong, Yalin Dong, Chang Ye
      Abstract: In this study, an innovative process, electrically assisted ultrasonic nanocrystal surface modification (EA-UNSM), is used to process Ti6Al4V alloy. As compared with traditional UNSM, EA-UNSM results in lower dislocation density and larger grains due to the thermal annealing effect caused by resistive heating. In addition, deeper plastic deformation layer is observed in the electrically assisted case. By supplying mechanical energy and thermal energy simultaneously, a strong dynamic precipitation effect is induced, which generates nanoscale precipitates in the EA-UNSM-treated Ti6Al4V alloy. These nanoscale precipitates can effectively pin dislocations during plastic deformation and thus significantly improve the surface hardness.Electrically assisted UNSM (EA-UNSM) takes advantages of high strain rate plastic deformation and dynamic precipitation, producing a unique structure with nanoscale grains and non-uniformly distributed nano-precipitates. It is observed that the pinning effect exerted by the nanoscale precipitates lead to stronger surfaces, though thermal annealing effect results in grain growth during EA-UNSM.
      PubDate: 2017-08-31T06:17:46.272777-05:
      DOI: 10.1002/adem.201700470
       
  • Characterization of Microstructure and Mechanical Properties of
           Mg–Y–Zn Alloys with Respect to Different Content of LPSO Phase
    • Authors: Klaudia Horváth; Daria Drozdenko, Stanislav Daniš, Gerardo Garcés, Kristián Máthis, Shae Kim, Patrik Dobroň
      Abstract: The Mg–Y–Zn alloys with different contents of alloying elements are extruded at an extrusion ratio of 4:1 at 350 °C. The microstructure of the alloys is of an inhomogeneous character showing fine grains produced due to dynamic recrystallization and coarse original grains elongated along the extrusion direction (ED). Moreover, Y and Zn form a long-period stacking-ordered (LPSO) phase whose volume fraction increases with their increasing content in the alloy. All investigated alloys exhibit distinct fiber textures with basal planes oriented parallel to ED. It is seen that increasing content of alloying elements leads to a weaker texture. Compression tests with concurrent acoustic emission (AE) measurements are performed along ED at room temperature and a constant strain rate in order to reveal active deformation mechanisms in the alloys and to relate them to their mechanical properties. The AE response is also discussed with respect to the volume fraction of the LPSO phase.Mg–Y–Zn alloys with a various content of alloying elements and thus a different volume fraction of the LPSO phase are investigated during compression along extrusion direction. Acoustic emission (AE) technique is applied for revealing the influence of the volume fraction of the LSPO phase on active deformation mechanisms. The volume fraction of the LPSO phase increases at the expense of the unrecrystallized grains what leads to suppressing the twinning activity.
      PubDate: 2017-08-31T06:10:35.967631-05:
      DOI: 10.1002/adem.201700396
       
  • Printing Polymer Nanocomposites and Composites in Three Dimensions
    • Authors: Rouhollah Dermanaki Farahani; Martine Dubé
      Abstract: Recent advances in materials science and three-dimensional (3D) printing hold great promises to conceive new classes of multifunctional materials and components for functional devices and products. Various functionalities (e.g., mechanical, electrical, and thermal properties, magnetism) can be offered by the nano- and micro-reinforcements to the non-functional pure printing materials for the realization of advanced materials and innovative systems. In addition, the ability to print 3D structures in a layer-by-layer manner enables manufacturing of highly-customized complex features and allows an efficient control over the properties of fabricated structures. Here, the authors present a brief overview mainly over the latest progresses in 3D printing of multifunctional polymer nanocomposites and microfiber-reinforced composites including the benefits, limitations, and potential applications. Only those 3D printing techniques that are compatible with polymer nanocomposites and composites, that is, materials that have already been used as printing materials, are introduced. The very hot topic of 3D printing of thermoplastic composites featuring continuous microfibers is also briefly introduced.Various state-of-the-art 3D printing methods compatible with polymer nanocomposite/composite materials are briefly reviewed in this mini-review paper. The paper aims to show that the integration of nano- and micro-reinforcements into 3D printing leads to the realization of innovative functional micro- and macro-devices for various applications such as MEMS, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems.
      PubDate: 2017-08-29T11:28:35.842624-05:
      DOI: 10.1002/adem.201700539
       
  • High Efficiency Poly(acrylonitrile) Electrospun Nanofiber Membranes for
           Airborne Nanomaterials Filtration
    • Authors: Riyadh Al-Attabi; Ludovic F. Dumée, Lingxue Kong, Jürg A. Schütz, Yosry Morsi
      Abstract: The potential of poly(acrylonitrile) electrospun membranes with tuneable pore size and fiber distributions were investigated for airborne fine-particle filtration for the first time. The impact of solution concentration on final membrane properties are evaluated for the purpose of designing separation materials with higher separation efficiency. The properties of fibers and membranes are investigated systematically: the average pore distribution, as characterized by capillary flow porometry, and thermo-mechanical properties of the mats are found to be dependent on fiber diameter and on specific electrospinning conditions. Filtration efficiency and pressure drop are calculated from measurement of penetration through the membranes using potassium chloride (KCl) aerosol particles ranging from 300 nm to 12 μm diameter. The PAN membranes exhibited separation efficiencies in the range of 73.8–99.78% and a typical quality factor 0.0224 (1 Pa−1) for 12 wt% PAN with nanofibers having a diameter of 858 nm. Concerning air flow rate, the quality factor and filtration efficiency of the electrospun membranes at higher face velocity are much more stable than for commercial membranes. The results suggest that the structure of electrospun membranes is the best for air filtration in terms of filtration stability at high air flow rate.This work investigates the fabrication of poly(acrylonitrile) (PAN) electrospun structures by varying the fiber diameter to offer specific pore size distributions and fiber morphologies for the capture of aerosol fine particles. The influence of the fiber diameter and membrane properties on the pressure drop and penetration depth of the particles is systematically evaluated. The PAN membranes exhibit separation efficiencies in the range of 73.8 to 99.78% and quality factors up to 0.024546 (1 Pa−1) for uniform nanofiber membranes made from 12 wt% PAN solution having an average fiber diameter of 858 nm.
      PubDate: 2017-08-29T11:28:26.629843-05:
      DOI: 10.1002/adem.201700572
       
  • Effect of Initial Annealing Temperature on Microstructural Development and
           Microhardness in High-Purity Copper Processed by High-Pressure Torsion
    • Authors: Saleh N. Alhajeri; Abdulla I. Almazrouee, Khaled J. Al-Fadhalah, Terence G. Langdon
      Abstract: The effect of the initial annealing temperature on the evolution of microstructure and microhardness in high purity OFHC Cu is investigated after processing by HPT. Disks of Cu are annealed for 1 h at two different annealing temperatures, 400 and 800 °C, and then processed by HPT at room temperature under a pressure of 6.0 GPa for 1/4, 1/2, 1, 5, and 10 turns. Samples are stored for 6 months after HPT processing to examine the self-annealing effects. Electron backscattered diffraction (EBSD) measurements are recorded for each disk at three positions: center, mid-radius, and near edge. Microhardness measurements are also recorded along the diameters of each disk. Both alloys show rapid hardening and then strain softening in the very early stages of straining due to self-annealing with a clear delay in the onset of softening in the alloy initially annealed at 800 °C. This delay is due to the relatively larger initial grain size compared to the alloy initially annealed at 400 °C. The final microstructures consist of homogeneous fine grains having average sizes of ≈0.28 and ≈0.34 µm for the alloys initially annealed at 400 and 800 °C, respectively. A new model is proposed to describe the behavior of the hardness evolution by HPT in high purity OFHC Cu.The effect of the initial annealing temperature on the evolution of microstructure and microhardness in Cu is investigated after processing by HPT. Copper alloys show rapid hardening and then strain softening in the very early stages of straining due to self-annealing. The final microstructures consist of homogeneous fine grains.
      PubDate: 2017-08-29T03:16:15.769868-05:
      DOI: 10.1002/adem.201700503
       
  • Microstructures and Tensile Properties of AZ91 Magnesium Alloys with Ca,
           Sm, and La Elements Additions
    • Authors: Li Fu; Xi Bo Wang, Pei Li Gou, Qi Chi Le, Wei Tao Jia, Yan Tang
      Abstract: Microstructures and tensile properties of as-cast and as-extruded AZ91 magnesium alloys with individual and combined additions of Ca, Sm, and La elements are investigated. The results show that Al2Ca, Al2Sm, and Al11La3 new phases form after adding Ca, Sm, La elements, decreasing the amount of Mg17Al12 phases and refining the microstructures. Microstructures of as-cast and as-extruded alloys with combined additions are significant refined. The Al2Ca and Al11La3 intermetallic compounds are crushed into granules because of severe deformation during hot extrusion, while the Al2Sm intermetallic compounds are not. Tensile tests results at room temperature indicate that individual additions of Ca, Sm, and La elements could increase the elongation of as-extruded alloys, and tensile tests results at 150 °C indicate that individual additions of Sm and La elements could increase the ultimate tensile strength and yield strength of as-extruded alloys. AZ91–0.3La alloy exhibits the best comprehensive tensile properties both at room temperature and 150 °C. However, combined additions in AZ91 alloys leads to coarseness and aggregation of Al2Sm phases, resulting in slightly decline of tensile properties both at room temperature and 150 °C.As-cast and as-extruded AZ91 alloys with additions of Ca, Sm, La elements are investigated to determine formation process of new phases, refinement in microstructures and improvement in tensile properties by analyzing the XRD patterns, optical metallurgical images, SEM images, and results of tensile tests both at room temperature and 150 °C. The refinement mechanisms in microstructure and tensile properties of these alloys after adding Ca, Sm, La elements are also discussed.
      PubDate: 2017-08-29T03:10:50.700461-05:
      DOI: 10.1002/adem.201700230
       
  • Editorial
    • Authors: Ehrenfried Zschech
      PubDate: 2017-08-29T01:00:45.805487-05:
      DOI: 10.1002/adem.201700444
       
  • Masthead: Adv. Eng. Mater. 8∕2017
    • PubDate: 2017-08-29T01:00:43.410716-05:
      DOI: 10.1002/adem.201770026
       
  • Back Cover: Advanced Engineering Materials 8∕2017
    • Abstract: 3D printing enables realisation of NdFeB based magnets in desired geometry with additional functionality like cooling channels that can make this magnet more suitable for various applications, and at the same time less dependent on expensive rare earth elements. This technology has capabilities to unlock the full potential of wind turbine generators, and boost the harvesting of renewable energy. Further details can be found in the article number 1700098.
      PubDate: 2017-08-29T01:00:41.672859-05:
      DOI: 10.1002/adem.201770029
       
  • Front Cover: Advanced Engineering Materials 8∕2017
    • Abstract: Chromium-rich oxide whiskers and nodules formed on the surface of an internal pore in additively-manufactured stainless steel, as discussed in article number 1700102 by Brad L. Boyce and co-workers. This internal porosity, caused by incomplete fusion of the source powder, results in low tensile ductility. The oxidation is thought to occur when porosity that connects to the free surface is exposed to the atmosphere during heat treatment.
      PubDate: 2017-08-29T01:00:35.023895-05:
      DOI: 10.1002/adem.201770025
       
  • Contents: Adv. Eng. Mater. 8∕2017
    • PubDate: 2017-08-29T01:00:34.602385-05:
      DOI: 10.1002/adem.201770027
       
  • Retracted: Effect of High-Energy Electropulsing on the Phase Transition
           and Mechanical Properties of Two-Phase Titanium Alloy Strips
    • Abstract: The above article in Advanced Engineering Materials (
      DOI : 10.1002/adem.201400273), published online on 10 December 2014 in Wiley Online Library (http://wileyonlinelibrary.com), has been retracted at the request of the corresponding author, Prof. Guoyi Tang, and with agreement fromauthors Zion T.H. Tse and Guolin Song, the journal Editor in Chief, and Wiley-VCH Verlag GmbH & Co. KGaA. The retraction has been agreed to for the following reason: according to an internal investigation carried out at Tsinghua University, the first author, Dr. Xiaoxin Ye, reused in this paper unreferenced data from previous publications by the same group of authors. The investigation also confirmed that the manuscript was submitted to the journal by Dr. Ye without the knowledge or approval of the other authors.ReferenceX. Ye, Z. T. H. Tse, G. Tang, G. Song, Adv. Eng. MaterM. 2015, 17, 995.
      DOI :10.1002/adem.201400273
      PubDate: 2017-08-29T01:00:33.457897-05:
       
  • Effects of Cu on Microstructures, Mechanical, and Magnetic Properties of
           Fe–Ni–P Alloys Fabricated by Liquid Phase Sintering
    • Authors: Runjian Jiang; Yang Hu, Guodong Cui, Chengsong Zhang, Ai Li
      Abstract: The Fe–Ni–P–Cu alloys with different copper content (0, 0.5, 1, and 2 wt%) are fabricated by liquid phase sintering (LPS) at 950 °C. The nano-Cu powder is mechanically mixed for 90 min with Fe–Ni–P composite powder using the ethanol as the medium. The microstructure, microhardness and compressive properties of Fe–Ni–P–Cu alloys are investigated. The results indicate that the copper is beneficial to improve the mechanical properties of sintered specimens. The sample contains a small amount of γ-(Fe, Ni) phase when the copper content is 1 wt%, which results in its the highest compressive yield strength (948.1 MPa). The highest microhardness of 371 HV is accessible in Fe–Ni–P–Cu alloy with 2 wt% Cu. The fracture surface analysis indicates that sintered specimens with Cu addition exhibit a typical intergranular mode.Fe–Ni–P–Cu alloys are prepared by liquid phase sintering of Ni–P coated iron and Cu powders. Cu addition improves the hardness and compressive yield strength of Fe–Ni–P–Cu alloy. The alloy with 1 wt% Cu has the highest compressive property and magnetic property. Decrease on γ-(Fe,Ni) phase content enhances the property of Fe–Ni–P–1 wt% Cu alloy.
      PubDate: 2017-08-25T02:00:32.123541-05:
      DOI: 10.1002/adem.201700404
       
  • A Triboelectric Self-Powered Sensor for Tire Condition Monitoring:
           Concept, Design, Fabrication, and Experiments
    • Authors: Hassan Askari; Zia Saadatnia, Amir Khajepour, Mir Behrad Khamesee, Jean Zu
      Abstract: This paper presents a novel type of triboelectric-based self-powered sensor for tire condition monitoring. The triboelectric based sensor is made of highly flexible, mechanically and thermally durable, and cost-effective polymeric materials. The authors firstly report the location inside of a tire for attaching the sensor to monitor tire conditions. Then, the authors analyze the performance of the sensor under different frequencies and stroke displacements to show the capability of the fabricated device as a self-powered sensor. Furthermore, the authors evaluate the durability and performance of the sensor to delineate its potential for tire condition monitoring. The results show that the fabricated self-powered sensor has the potential of measuring the tire forces and pressure. The use of the proposed sensor for tire condition monitoring systems (TCMS) can be considered as a significant step toward developing smart tires, improving vehicles control strategy, and accordingly, enhancing passengers safety.Triboelectric Nano Generator for Tire Condition Monitoring: As the figure shows, with attaching a new sensory device to a tire, we can obtain crucial information pertinent to its dynamics. The use of the proposed sensor for tire condition monitoring systems (TCMS) is a significant step toward developing smart tires, improving vehicles control strategy, and accordingly, enhancing passengers safety and reduction of disastrous accidents.
      PubDate: 2017-08-24T13:10:27.538505-05:
      DOI: 10.1002/adem.201700318
       
  • Role of Grain Boundary Sliding in Texture Evolution for Nanoplasticity
    • Authors: Yajun Zhao; Laszlo S. Toth, Roxane Massion, Werner Skrotzki
      Abstract: A new crystal plasticity model is presented to account for the effect of grain boundary sliding (GBS) on texture evolution during large plastic deformation of nanocrystalline materials. In the model, 12 grain boundaries are assigned for each grain and their sliding rates are calculated using Newtonian viscoplasticity. The lattice rotation of the grain interior is computed by taking into account the deformation field modification produced by GBS. The model is employed for predicting the texture evolution in a nanocrystalline Pd–10 at%Au alloy subjected to large strain simple shear, up to a shear strain of 16.8. Two main texture effects due to increasing GBS are identified: high reduction in texture intensity, and tilts of the texture components from their ideal orientations. In the alloy considered, the contribution of GBS to the total strain is identified to be about 30%.A new crystal-plasticity model is proposed to study the effect of grain boundary sliding (GBS) on texture evolution for nanocrystalline materials under large plastic deformation. The GBs for each grain are modeled by flat planes, constructing a polyhedron (shown in the figure). Quantitatively, the role of GBS in texture evolution is found: the randomization of texture and the tilts of the texture components from their ideal positions.
      PubDate: 2017-08-23T12:36:21.474747-05:
      DOI: 10.1002/adem.201700212
       
  • A Hierarchically Porous Carbon Fabric for Highly Sensitive Electrochemical
           Sensors
    • Authors: Yuan Jiao; Seong Won Cho, Suyoun Lee, Sang Hoon Kim, Seung-Yeol Jeon, Kahyun Hur, Sun Mi Yoon, Myoung-Woon Moon, Aiying Wang
      Abstract: The hierarchically porous carbon fabrics with controlled conductivity and hydrophilicity have been fabricated by dual templating method of soft templates nested on hard templates. A non-woven fabric coated with a solution of F127/resol has been carbonized for the synthesis of both macro-porous structures of 10–15 µm in diameter having meso-porous carbon structures of 4–6 nm, respectively. After carbonization treatment, not only conductivity is significantly improved, the hierarchically porous carbon also shows superhydrophilicity or water-absorbing nature due to mild hydrophilic material and its dual scale roughness. The porous carbon becomes conductive with resistivity widely tuned from 5.4 × 103 Ωm to 3.1 × 10−3 Ωm by controlling the carbonization temperature. As the increased wettability for organic liquids could lead organic molecules deep into carbonized fabrics, the sensitivity of hierarchically porous carbon fabrics benefits the detection for methanol(CH3OH) or hydrogen peroxide (H2O2). This new design concept of hierarchically porous structures having the multi-functionality of high wettability and conductivity can be highly effective for electroanalytical sensors.Hierarchical porous carbon fabrics with controlled conductivity and hydrophilicity have been fabricated by dual templating. The hydrophilicity and conductivity work synergistically, making the porous carbon material a good candidate for electrochemical sensor.
      PubDate: 2017-08-23T12:35:25.573332-05:
      DOI: 10.1002/adem.201700608
       
  • Durable and Recyclable Superhydrophobic Fabric and Mesh for
           Oil–Water Separation
    • Authors: Shaher Bano; Usama Zulfiqar, Usama Zaheer, Muhammad Awais, Iftikhar Ahmad, Tayyab Subhani
      Abstract: The authors report durable and recyclable nanocomposite superhydrophobic coatings on two different substrates of fabric and mesh as prepared by titania nanoparticles and polydimethysiloxane (PDMS). The felted wool fabric and the steel mesh are initially coated with a thin layer of PDMS, which is followed by the deposition of nanocomposite coating of titania nanoparticles embedded in PDMS. The dual surface modification of two kinds of substrates generates highly hydrophobic surface character, which is retained after durability performance as measured in ultrasonication, sand, and emery paper abrasion tests. Oil–water separation experiments are performed using water mixtures with four oils, that is, n-hexane, toluene, kerosene, and diesel to ensure the industrial applications of prepared composite materials. Moreover, nanocomposite coatings are tested for several cycles of oil–water separation in harsh conditions such as hot water, sodium chloride, and hydrochloric acid. The adopted approach improves the separation performance by inducing durability of the prepared nanocomposite coatings along with introducing recyclable character.Durable, recyclable, and superhydrophobic nanocomposite coatings are prepared on fabric and steel mesh. The coatings comprise titania nanoparticles and polydimethylsiloxane (PDMS). The substrates are initially coated with PDMS, followed by deposition of titania/PDMS nanocomposite coating. The resulting highly hydrophobic materials are utilized for the separation of oil–water mixtures.
      PubDate: 2017-08-21T03:16:12.906094-05:
      DOI: 10.1002/adem.201700460
       
  • Ag@Sn Core-Shell Powder Preform with a High Re-Melting Temperature for
           High-Temperature Power Devices Packaging
    • Authors: Fuwen Yu; Bin Wang, Qiang Guo, Xin Ma, Mingyu Li, Hongtao Chen
      Abstract: In this paper, the authors propose a highly conductive die attach material based on Ag@Sn powder for power devices operating at high temperatures or in other harsh environments. The preform can be reflowed at 250 °C (18 °C above the Tm of Sn, 232 °C), but the resulting bondline can sustain high temperatures up to 400 °C with a high shear strength due to the high re-melting temperature of the formed Ag3Sn (Tm = 480 °C) after the complete consumption of the outer Sn layers. In addition, the formed bondline exhibits excellent electrical and thermal conductivities due to the embedded Ag particles in the interconnections. The interconnections also exhibit excellent reliability under thermal shock cycling from −55 to 200 °C because of the increased bondline thickness and inherent ductility of the Ag particles embedded in the Ag3Sn.Ag@Sn Core-shell Powder Preforms is successfully prepared, the preforms required only a short time (5 min) reflow processing at 250 °C, but the resulting interconnections can withstand a high temperature up to 480 °C and exhibit excellent electrical and thermal conductivities due to the high density and the embedded Ag particles in the interconnections.
      PubDate: 2017-08-17T08:00:42.206592-05:
      DOI: 10.1002/adem.201700524
       
  • Effect of Creep and Aging on the Precipitation Kinetics of an Al-Cu Alloy
           after ne Pass of ECAP
    • Authors: Markus Härtel; Philipp Frint, Kevin G. Abstoss, Martin F.-X. Wagner
      Abstract: Recent work shows that severe plastic deformation processes such as ECAP or HPT considerably accelerate the precipitation kinetics of Al-Cu alloys. In this study, the authors analyze how a combination of mechanical load, aging time (and increased plastic strain), and aging temperature affects the precipitation kinetics of an AA2017 alloy after ECAP. After solution annealing, the material is processed by one pass of ECAP (120°-channel angle) at 140 °C. Compressive creep tests are performed on the initial condition and the ECAP-deformed material. The resulting microstructures are studied in detail using electron microscopy. To investigate the influence of mechanical loading, interrupted compressive creep tests are performed and compared with aged samples (produced without any mechanical loading at the same temperature and after the same amount of time). By keeping time and load constant in another set of interrupted compressive creep tests, the influence of temperature is investigated. Our study shows that increasing mechanical loading further accelerates the precipitation kinetics. Temperature accelerates the precipitation kinetics as well, but results in coarser precipitates. The authors also find that different creep strains can lead to the formation of two different regions in the microstructure: regions with only a few coarsened θ-phase precipitates, and regions with numerous, finely dispersed precipitates.The authors analyze how a combination of mechanical load, aging time, and temperature affects the precipitation kinetics of AA2017 after ECAP. The authors find that different creep strains lead to the formation of two different regions in the microstructure: regions (A) with only a few coarsened θ-phase precipitates, and regions (B) with numerous, finely dispersed precipitates.
      PubDate: 2017-08-17T07:50:41.475951-05:
      DOI: 10.1002/adem.201700307
       
  • Influence of Ultrafine-Grained Layer on Gaseous Nitriding of Large-Sized
           Titanium Plate
    • Authors: Quantong Yao; Jian Sun, Guanglan Zhang, Weiping Tong, Liang Zuo
      Abstract: In this paper, mechanical shot blasting on a large sized titanium plate is conducted to induce severe plastic deformation, which generates an ultrafine-grained surface layer. The effect of an ultrafine-grained layer on nitriding is evaluated at nitriding temperatures from 600 to 850 °C. The structural phases and mechanical property improvements are investigated and compared to those of a coarse-grained specimen by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and mechanical property measurements. The results indicate that an ultrafine-grained layer enhances the nitriding kinetics and produces a thicker nitrided layer than that of a coarse-grained plate at the same gaseous nitriding temperatures. The improved kinetics are attributed to a greater number of grain boundaries and defects introduced into the titanium plate surface by the mechanical shot blasting treatment. Meanwhile, the surface and cross-sectional hardness values improve compared to the coarse-grained plate due to the thicker nitrided layer resulting from deeper nitrogen diffusion.The authors firstly investigat the effect of ultrafine-grained layer on gaseous nitriding of large titanium plate. The results show that the nitrided thickness of the ultrafine-grained plate is thicker than that of the coarse-grained plate at each nitriding temperature, and the greatest difference between the MSB treated and coarse-grained plates occur at 750 °C.
      PubDate: 2017-08-15T02:41:09.106979-05:
      DOI: 10.1002/adem.201700455
       
  • Phase-Field Modeling of Microstructural Evolution by Freeze-Casting
    • Authors: Tsung-Hui Huang; Tzu-Hsuan Huang, Yang-Shan Lin, Chih-Hsiang Chang, Po-Yu Chen, Shu-Wei Chang, Chuin-Shan Chen
      Abstract: Freeze-casting has attracted great attention as a potential method for manufacturing bioinspired materials with excellent flexibility in microstructure control. The solidification of ice crystals in ceramic colloidal suspensions plays an important role during the dynamic process of freeze-casting. During solidification, the formation of a microstructure results in a dendritic pattern within the ice-template crystals, which determines the macroscopic properties of materials. In this paper, the authors propose a phase-field model that describes the crystallization in an ice template and the evolution of particles during anisotropic solidification. Under the assumption that ceramic particles represent mass flow, namely a concentration field, the authors derive a sharp-interface model and then transform the model into a continuous initial boundary value problem via the phase-field method. The adaptive finite-element technique and generalized single-step single-solve (GSSSS) time-integration method are employed to reduce computational cost and reconstruct microstructure details. The numerical results are compared with experimental results, which demonstrate good agreement. Finally, a microstructural morphology map is constructed to demonstrate the effect of different concentration fields and input cooling rates. The authors observe that at particle concentrations ranging between 25 and 30% and cooling rate lower than −5° min−1 generates the optimal dendrite structure in freeze casting process.A phase-field model is developed to investigate microstructural evolution by the freeze-casting process. Under the assumption that the colloidal particles can be represented by a concentration field, the interfacial condition of mass conservation, the Gibbs-Thomson condition, and particle segregation can be naturally included in the model. The morphology of dendritic ice crystal and accumulation of ceramic particles are accurately captured.
      PubDate: 2017-08-14T01:56:18.93774-05:0
      DOI: 10.1002/adem.201700343
       
  • Small Y Addition Effects on Hot Deformation Behavior of Copper-Matrix
           Alloys
    • Authors: Yi Zhang; Huili Sun, Alex A. Volinsky, Bingjie Wang, Baohong Tian, Zhe Chai, Yong Liu, Kexing Song
      Abstract: Hot deformation behavior of two alloys, Cu–Zr and Cu–Zr–Y is studied by compression tests using the Gleeble-1500D thermo-mechanical simulator. Experiments are conducted at 550–900 °C temperature and 0.001–10 s−1 strain rate. The true stress–true strain curves are analyzed, and the results show that the flow stress strongly depends on the temperature and the strain rate. Furthermore, both alloys behave similarly when the flow stress increases with higher strain rate and lower temperature. Based on the dynamic material model, the processing maps are obtained at strains of 0.4 and 0.5. The optimal processing parameters for the Cu–Zr and Cu–Zr–Y alloys are determined. In addition, the constitutive equations for the alloys are established to characterize the flow stress as a function of strain rate and deformation temperature. Based on the microstructure evolution analysis, the results show that the addition of Y can effectively promote dynamic recrystallization. Moreover, the processability of the alloy can be optimized. Thermal deformation activation energy and the peak power dissipation efficiency for the alloys are obtained. It is observed that the addition of Y effectively improves thermal deformation activation energy and has considerable influence on the peak power dissipation efficiency.The addition of Y to the Cu–Zr alloy effectively promotes dynamic recrystallization and improves thermal deformation activation energy, having a considerable influence on the peak power dissipation efficiency.
      PubDate: 2017-08-14T01:51:17.283951-05:
      DOI: 10.1002/adem.201700197
       
  • Indentation Response and Structure-Property Correlation in a Bimodal
           Ti–6Al–4V Alloy
    • Authors: Indrani Sen; Shibayan Roy, Martin F.-X. Wagner
      Abstract: Understanding the deformation behavior of multi-phase alloys under external loading requires careful mechanical characterization of the individual constituent phases at various length scales. The present study first evaluates the elastic moduli and hardness of the microstructural constituents viz. primary α (αp) and transformed β (secondary α (αs) plus retained prior β) phases in a bimodal Ti–6Al–4V alloy by nano-indentation using different loads. The bulk mechanical properties of the overall microstructure are then determined by grid wise nano-indentation, as well as micro-indentation. The alloy shows a pronounced indentation size effect; the hardness increases with the decrease in indentation load, or depth of penetration. Assuming an iso-stress condition for individual constituents (αp and transformed β) in the rule of mixture approach, the bulk mechanical properties of the Ti–6Al–4V alloy are reasonably predicted. Such prediction of bulk properties, however, is not possible when a similar calculation is performed using iso-strain condition. The transformed β phase shows disparity between the estimated and experimental values, while considering the αs and β phases individually, on both iso-stress and iso-strain assumptions. From these results, the influence of individual microstructural phases (size, distribution, volume fraction, morphology) and the interfaces between them, is found key in controlling the overall bulk mechanical response of the alloy system.The study evaluates mechanical properties of microstructural constituents in a bimodal Ti–6Al–4V alloy by nano- and micro-indentation. The role of size, distribution, morphology, volume fraction, and interfaces of these constituents in controlling the bulk mechanical response is rationalized by a rule of mixture based theoretical calculation.
      PubDate: 2017-08-14T01:50:38.91002-05:0
      DOI: 10.1002/adem.201700298
       
  • Work of Adhesion Measurements of MoS2 Dry Lubricated 440C Stainless Steel
           Tribological Contacts
    • Authors: Simo Pajovic; Guillaume Colas, Aurélien Saulot, Mathieu Renouf, Tobin Filleter
      Abstract: The tribological behavior of dry lubricants depends on their mechanical and physicochemical environment, making it difficult to predict in practice. Discrete Element Method-based modeling has been one successful approach to provide valuable insight into the tribology of dry lubricated contacts. However, it requires well-defined interactions between discrete elements, in particular between those simulating different materials. Measuring the properties governing those interactions, such as the work of adhesion (W), is therefore critical. The present work describes a method for measuring the W between AISI440C steel and MoS2-based coatings used in spacecraft. Using Atomic Force Microscopy local asperity and adhesion measurements, the W between steel microbeads and MoS2 coatings is determined at different stages in its wear life. The distributions of W values in the worn coatings and pristine coatings agree well with earlier Time-of-Flight Secondary Ion Mass Spectroscopy studies on the physicochemistry of the samples, as well as contact angle measurements. Additional measurements between the same materials on a ball bearing from a real life-test unit of a spacecraft instrument also show a similar W distribution, suggesting that the approach used here provides relevant data for use in numerical simulations.The study describes a method for measuring the work of adhesion (W) between AISI440C steel and MoS2-based coatings. After morphological and chemical studies of the surfaces, W is determined at different stages of the coating's wear life by using Atomic Force Microscopy (AFM), local asperity detection, and adhesion measurements with steel microbeads.
      PubDate: 2017-08-10T08:44:24.551971-05:
      DOI: 10.1002/adem.201700423
       
  • Nanoporous Metals with Structural Hierarchy: A Review
    • Authors: Theresa Juarez; Juergen Biener, Jörg Weissmüller, Andrea M. Hodge
      Abstract: Nanoporous (np) metals have generated much interest since they combine several desirable material characteristics, such as high surface area, mechanical size effects, and high conductivity. Most of the research has been focused on np Au due to its relatively straightforward synthesis, chemical stability, and many promising applications in the fields of catalysis and actuation. Other materials, such as np-Cu, Ag, and Pd have also been studied. This review discusses recent advances in the field of np metals, focusing on new research areas that implement and leverage structural hierarchy while using np metals as their base structural constituents. First, we focus on single-element porous metals that are made of np metals at the fundamental level, but synthesized with additional levels of porosity. Second, we discuss the fabrication of composite structures, which use auxiliary materials to enhance the properties of np metals. Important applications of these hierarchical materials, especially in the fields of catalysis and electrochemistry, are also reviewed. Finally, we conclude with a discussion about future opportunities for the advancement and application of np metals.This review discusses developments in the field of nanoporous metals, focusing on research areas that implement and leverage structural hierarchy while using nanoporous metals as the base structural constituents. Fabrication methods for both single elemental materials and composites are reviewed followed by a discussion of emerging applications.
      PubDate: 2017-08-09T06:25:58.3624-05:00
      DOI: 10.1002/adem.201700389
       
  • Enhancing the Strength and Ductility in Mg–Zn–Ce Alloy through
           Achieving High Density Precipitates and Texture Weakening
    • Authors: Yuzhou Du; Mingyi Zheng, Xiaoguang Qiao, Bailing Jiang
      Abstract: The microstructure with weak fiber texture and dense precipitates is designed and produced through extrusion and subsequent ageing treatment of Mg–6Zn–0.2Ce (wt%) alloy. Results show that ageing treatment improves the strength of the as-extruded Mg–6Zn–0.2Ce (wt%) alloy and retains the ductility. The peak-aged alloy exhibits a good combination of strength and ductility, which is superior to the commercial Mg alloy. The yield strength and elongation to fracture of the peak-aged Mg–6Zn–0.2Ce (wt%) alloy are 225 MPa and 32.1%, respectively. The strength improvement of the peak-aged alloy is attributed to dense rod-like precipitates, and the superior ductility is mainly due to weaker texture and homogeneous microstructure.The microstructure with weak fiber texture and dense precipitates is produced through extrusion and subsequent ageing treatment of Mg–6Zn–0.2Ce (wt%) alloy. The peak-aged alloy exhibits a good combination of strength and ductility with the yield strength of 225 MPa and elongation to fracture of 32.1%, which is attributed to dense rod-like precipitates and weaker texture.
      PubDate: 2017-08-08T07:01:55.226185-05:
      DOI: 10.1002/adem.201700487
       
  • Effect of Trace B on the Microstructure and Mechanical Properties of a
           Newly Near α High Temperature Titanium Alloy
    • Authors: Chongxiao Guo; Changjiang Zhang, Jianchao Han, Shuzhi Zhang, Fei Yang, Lihua Chai, Ziyong Chen
      Abstract: In this study, the microstructural evolution and mechanical properties of a newly near α titanium alloy with trace additions of B by in situ casting route are investigated. The results show that the coarse prior β grain and α lath within matrix alloy are gradually refined with increasing of B addition. The relative refinement mechanism of prior β grain and α lath width is analyzed and discussed. In addition, it is shown that both of ultimate compressive strength (UCS) and yield strength (UYS) increase with B addition, which is mainly attributed to microstructural refinement. However, the compressive ductility and fracture toughness decrease with increasing of B addition, which is due to the cracking of TiB, leading to the acceleration of crack extension.A newly near α titanium alloy with trace addition of B are discussed. Necklace-like of TiB locates at the grain boundary of prior β–Ti. According to the solidification path of B-containing alloys, refinement mechanism is elaborated. Ultimate compressive strength and yield strength increase, while the compressive ductility and fracture toughness decrease with B addition.
      PubDate: 2017-08-08T07:01:50.525811-05:
      DOI: 10.1002/adem.201700490
       
  • Superplastic Property of the Ti–6Al–4V Alloy with Ultrafine-Grained
           Heterogeneous Microstructure
    • Authors: Hiroaki Matsumoto; Takuro Nishihara, Vincent Velay, Vanessa Vidal
      Abstract: Ti–6Al–4V alloy having a heterogeneous microstructure composed of ultrafine-equiaxed-α-grains and fine-lamellar-α-grains is investigated for microstructural changes during superplastic deformation at temperature of 700 °C. The Ti–6Al–4V alloy having an optimum fraction of fine-lamellar-α-grains exhibits an excellent superplastic property and the highest elongation of 583% (tested at 700 °C 10−3 s−1). This is mainly due to the optimized activation of grain-boundary-sliding and additional accommodation mechanism associated with frequent occurrences of dynamic recrystallization and β precipitation at boundaries during deformation of the heterogeneous starting microstructure. The present result suggests the possibility that optimizing the starting microstructure so as to have an optimum heterogeneous-microstructure serves as an additional stress accommodation mechanism and leads to a large superplastic elongation.The ultrafine-grained Ti–6Al–4V alloy having an optimum fraction of highly-elongated-α-grains exhibits the highest tensile elongation of 583% (tested at 700 °C 10–3 s–1). This is mainly due to the optimized activation of grain-boundary-sliding and additional accommodation mechanism associated with frequent occurrences of dynamic recrystallization and β precipitation at boundaries during deformation of the heterogeneous starting microstructure.
      PubDate: 2017-08-08T07:01:17.099619-05:
      DOI: 10.1002/adem.201700317
       
  • Remarkable Improvement of Damping Capacity of Mn–20Cu–5Ni–2Fe (at%)
           Alloy by Zinc Element Addition
    • Authors: Dong Li; Wenbo Liu, Ning Li, Jiazhen Yan, Sanqiang Shi
      Abstract: In this paper, the effect of Zn element addition on martensitic transformation and damping capacity of Mn–20Cu–5Ni–2Fe (at%, M2052) alloy has been investigated systematically by using X-ray diffraction, optical microscopy, and dynamic mechanical analyzer. The results show that martensitic transformation and damping capacity have a crucial dependence on the addition of Zn element. It not only can markedly enhance the damping capacity of M2052 alloy at room temperature (internal friction Q−1 increases by ≈23% compared to M2052 without Zn as strain amplitude reaches 4 × 10−4), but also reduces the attenuation of damping capacity effectively at elevated temperatures. This is mainly because the addition of Zn element can evidently increase the Gibbs free energy difference between γ parent phase and γ' phase produced by face centered cubic to face centered tetragonal (f.c.c-f.c.t) phase transformation, and then raises the martensitic transformation and its reverse transformation temperatures, eventually leading to the apparent increase of amount of f.c.t γ' phase micro-twins as damping source and the significant enhancement of damping capacity. It will be of great value for design and optimization of high-performance M2052 damping alloy toward practical applications.In this paper, the effect of Zn addition on martensitic transformation and damping capacity of M2052 alloy is investigated. Results show that it not only can markedly enhance the damping capacity of M2052 at room temperature, but reduces the attenuation of damping capacity effectively at elevated temperatures. This is because the Zn addition can raises the Ms from 50° C up to 58° C, thus leading to the increase of amount of f.c.t γ′ phase micro-twins as damping source.
      PubDate: 2017-08-07T06:55:31.118121-05:
      DOI: 10.1002/adem.201700437
       
  • Fracture Mode Transition in Nb–1Si Alloys Triggered by Annealing
           Heat Treatment
    • Authors: Bin Kong; Lina Jia, Songxin Shi, Yueling Guo, Hu Zhang
      Abstract: The concentration of Si plays a crucial role in the ductile-brittle transition of Nb solid solution (NbSS) alloys, and an appropriate annealing treatment contributes to controlling the Si concentration in NbSS alloy. In this paper, Nb–1Si (at%) alloy is arc-melted and annealed at different temperature (1300, 1400, and 1500 °C) for 10 h. After annealing, both the strength and ductility increase. Particularly, after annealing at 1300 °C, the fracture feature transforms from cleavage to dimples, and the alloy possesses good strength and retains decent ductility due to the low Si concentration and small-sized intragranular Nb3Si particles precipitating in the NbSS. The significant effect of annealing on the fracture mechanism of Nb–1Si provides guidance for the design of Nb–Si based alloys.The arc-melted Nb–1Si (at%) alloy (AM) fails in a brittle cleavage manner, mainly due to the embrittlement of Si and the plastic constraint imposed by the large silicides present in the eutectic compositions. After annealing at 1300 °C for 10 h (HT1300), the Si concentration in the NbSS decreases and submicron Nb3Si particles precipitate. As a result, the strength and elongation improve, and transition from a cleavage fracture to a dimple fracture occurs.
      PubDate: 2017-08-07T01:20:57.567511-05:
      DOI: 10.1002/adem.201700442
       
  • Temperature Effect on Performance of Triboelectric Nanogenerator
    • Authors: Cun Xin Lu; Chang Bao Han, Guang Qin Gu, Jian Chen, Zhi Wei Yang, Tao Jiang, Chuan He, Zhong Lin Wang
      Abstract: The triboelectric nanogenerator (TENG) is a promising energy harvesting technology that can convert mechanical energy into electricity and can be used as self-powered active sensors. However, previous studies are mostly carried out at room temperature without considering the temperature effect on the electrical performance of TENGs, which is critical for the application of electronics powered by TENGs in different regions in the world. In the present work, a TENG that worked in the single-electrode and contact-separation mode is utilized to reveal the influence of environment temperature on the electrical performance of TENG. The electrical performance of the TENG shows a decreasing tendency, as the temperature rises from −20 to 150 °C, which is controlled by the temperature-induced changes in the ability of storing and gaining electrons for polytetrafluoroethylene (PTFE). The storing electron ability change of PTFE is attributed to two aspects: one is the reduction of relative permittivity of PTFE sheet as the temperature increases, and the other is the variations of effective defects such as the escape of trapped charges in shallow traps and surface oxidation under the effect of temperature perturbation. This work can provide useful information for the application of TENG in both electric power generation and self-powered sensors in the harsh environment.We propose the temperature-induced effect on performance of triboelectric nanogenerator (TENG). The electrical performance of TENG is found to decrease with the increase of temperature. This temperature-induced effect on electrical performance of TENG is caused by following two reasons. 1) The changes of relative permittivity of the PTFE sheet. 2) The variation of electron traps such as the escape of trapped electric charges in shallow traps and surface oxidation under the effect of temperature perturbation.
      PubDate: 2017-08-07T01:20:28.765891-05:
      DOI: 10.1002/adem.201700275
       
  • Active Control of Microstructure in Powder-Bed Fusion Additive
           Manufacturing of Ti6Al4V
    • Authors: Guglielmo Vastola; Gang Zhang, Qing Xiang Pei, Yong-Wei Zhang
      Abstract: Because of the complex interactions among the energy beam, the powder bed, and the material phase transformations, powder-bed fusion additive manufacturing is very sensitive to process parameters, such as beam power and scan speed. As a result, the process window to produce fully-dense, ASTM-grade components is narrow. In such scenario, envisioning further control of mechanical properties is very challenging. As a departure from traditional attempts to control microstructure by changing the process parameters, the authors propose the introduction of a thermoelectric module (TEM) as an active device inside the build chamber. Using process modeling, the authors show that by altering the heat flow into the material through the TEM device, the volume fraction of martensite can be controlled in its entire range. In particular, the authors show that modern TEM modules can deliver sufficient thermal power to block the formation of martensite. As a result, microstructure can be controlled locally while retaining the beam power and scan speed optimal for part density and surface finish. While the results are demonstrated for Ti6Al4V and the electron beam melting process, the concept is general and, in principle, applicable to other materials and machines systems such as IN781 and selective laser melting.As a departure from traditional attempts to control microstructure, the authors propose the introduction of a thermoelectric module (TEM) as an active device inside additive manufacturing. The authors show that by altering the heat flow into the material through the TEM device, the volume fraction of martensite can be controlled. The concept is general and applicable to other materials and machines systems.
      PubDate: 2017-08-07T01:10:24.174339-05:
      DOI: 10.1002/adem.201700333
       
  • Investigation on the Controllable Microstructures of High Iron Content
           Al–Fe Alloys Fabricated via Solid–Liquid Mixture Method Combining with
           Plasma Arc Heating Approach
    • Authors: Yuli Zhou; Jian Wang, Mingyang He, Lin Gu, Peihua Wangyang
      Abstract: Al–Fe alloys, with large amounts of sphere-like structures, few plate-like structures, and little needle-like structures of micron scale second phase have been successfully prepared via a new type of solid–liquid mixture approach combined with plasma arc heating (PAH). The authors have obtained Al–Fe alloys with iron content of 0–15%, which is of extremely significance that thermal plasma jet (TPJ) breaks through the limitation of low iron content in Al–Fe alloys. Microstructures characterization indicates that not only the microstructures of Al–Fe alloys are refined, but also the morphologies are optimized. Meanwhile, sharp corners of iron powders are rounded off and impurities are removed under the action of PAH, which is important for improving mechanical property of Al–Fe alloys. And then, the effects of various parameters including PAH, iron content, and melt temperature on the microstructures and mechanical performance are systematically investigated. The possible influence mechanisms of parameters are investigated and put forward, and appropriate parameters have been obtained during the processing of Al–Fe alloys via TPJ.Al–Fe alloys with sphere-like Al3Fe, which own excellent mechanical performance, have been fabricated via solid–liquid mixture method combined with plasma arc heating approach. Meanwhile, the effects of various parameters involving PAH, iron content, and melt temperature on the microstructures and mechanical performance are systematically investigated. The possible influence mechanism of parameters in fabricating Al–Fe alloys have been further investigated.
      PubDate: 2017-08-04T06:45:35.837-05:00
      DOI: 10.1002/adem.201700426
       
  • A Review of Gold and Silver Nanoparticle-Based Colorimetric Sensing Assays
    • Authors: Myalowenkosi Sabela; Sebastien Balme, Mikhael Bechelany, Jean-Marc Janot, Krishna Bisetty
      Abstract: The nanoparticle colorimetric-based methods have been extensively used for rapid detection, however there are few limitations which can be kept under control or avoided by understanding the crucial parameters involved in these reactions. This review addresses the main parameters that influence colorimetric-based methods and provides a rational classification of the current approaches, by focusing particularly on gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs). The AgNP and AuNP-based colorimetric assays can be very efficient and sensitive especially for biomolecule identification and for metal ion detection in environmental screening. Specifically, this review highlights the detection of metal ions through their coordination with nanoparticle stabilizing ligands. The review also addresses various approaches based on label-free aptasensors to better understand their role as smart colorimetric sensing devices.This review addresses the main parameters that influence the nanoparticle colorimetric-based methods for rapid detection of biomolecules and metal ion in environmental screening. It provides a rational classification of the current approaches by focusing particularly on gold and silver nanoparticles.
      PubDate: 2017-08-03T06:06:07.945763-05:
      DOI: 10.1002/adem.201700270
       
  • Strengthening Nickel by In Situ Graphene Synthesis
    • Authors: Kaihao Zhang; Matthew Poss, Ping-Ju Chen, Sameh Tawfick
      Abstract: Owing to the superior strength and atomic thickness of graphene, it can in theory reinforce metals beyond the usual rule of mixtures bounds by constraining dislocations motion and strain localization at the grain boundaries. This unusual enhancement relies on the graphene's ability to conform to and wrap metal grains. This study experimentally probes the limits of this behavior and investigates the role of interface in designing superior graphene composites. Free-standing nickel–multilayer graphene (Ni–MLG) nanomembranes are fabricated by in situ chemical vapor deposition. Using nanoindentation, elastic modulus (285.16 GPa), maximum stress (2.35 GPa), and toughness (1407.26 Jm−2) are measured, and these values exceed the rule of mixtures bounds. The multi-frequency atomic force microscopy (AFM) is used to spatially map the elastic properties and topography of the MLG on Ni grain boundaries. This emerging characterization reveals that effective reinforcement is achieved when graphene conforms and bridges the grain texture. Nanoindentation and AFM confirm that these mechanisms are ineffective in non-conformally attached Ni–MLG composites, which exhibit significantly weaker mechanical behavior. These results guide the design of effective graphene composites by highlighting the importance of nanoscale roughness and interfaces, and clearly demonstrate the superiority of composite processing routes based on in situ graphene synthesis.Multi-functional nickel–multilayer graphene (Ni–MLG) composite thin film with ultra-high elastic modulus, strength, and toughness are readily synthesized via in situ chemical vapor deposition. The nanoscale surface roughness and the resulting conformal interface between nickel and graphene renders the strengthening and toughening of composite thin film.
      PubDate: 2017-08-02T07:10:36.835059-05:
      DOI: 10.1002/adem.201700475
       
  • Ferromagnetic Film − Substrate Decoupling for Sensor Applications
    • Authors: Stefan Beirle; Klaus Seemann, Harald Leiste, Sven Ulrich
      Abstract: This study presents the decoupling of ferromagnetic properties of Fe–Co–Hf–N films with an in-plane uniaxial anisotropy from ferromagnetic cemented carbide (WC–Co) substrates by predepositing a non-ferromagnetic buffer layer between the substrate and the film. Due to the ferromagnetic Co content in the substrate, a magnetic coupling effect arises which suppresses the natural ferromagnetic resonance of the Fe32Co45Hf11N12 film at a frequency of 2.13 GHz. The deposition of a non-ferromagnetic, electrically conductive TiN layer, or a non-ferromagnetic, electrically insulating SiO2 layer between the substrate and the soft ferromagnetic film shows decoupling regarding the static ferromagnetic properties, so that the formation of an in-plane uniaxial anisotropy is possible. With regard to the application as a high-frequency sensor the paper shows that with increasing the thickness of the electrically insulating SiO2 buffer layer the full width at half maximum (FWHM) of the resonance line becomes much sharper, in contrast to the electrically conductive TiN. The explanation was attributed to the formation of eddy-currents in the electrically conductive material causing a magnetic field which disturbs the uniform precession of the magnetic moments. The high-frequency properties of the decoupled film system are promising for a thermal and mechanical stress sensor system on cutting tools.Decoupling the soft ferromagnetic properties of Fe–Co–Hf–N films with an in-plane uniaxial anisotropy from hard ferromagnetic cemented carbide substrates (WC–Co) is promising for the realization of a thermal and/or mechanical stress sensor system on cutting tools. One part is to provide a magnetostrictive film system which allows to measure the natural ferromagnetic resonance. The present paper shows a way to decouple the ferromagnetic film from the substrate and demonstrates how the FWHM of the resonance line can be tuned.
      PubDate: 2017-08-02T01:55:54.274601-05:
      DOI: 10.1002/adem.201700397
       
  • Processing Induced Flaws in Aluminum–Alumina Interpenetrating Phase
           Composites
    • Authors: Michał Basista; Justyna Jakubowska, Witold Węglewski
      Abstract: This review paper deals with flaws in aluminum–alumina composites and FGMs induced by their manufacturing processes. Aluminum–alumina composites have been studied for many years as potentially interesting materials for applications, for example, in the automotive sector due to their enhanced mechanical strength, wear resistance, good heat conductivity and low specific weight. The focus here is on the interpenetrating phase composites (IPCs) manufactured by infiltration of porous alumina preforms with molten aluminum alloys. The primary objective is to provide an updated overview of research findings on a variety of flaws occurring at different stages of the manufacturing processes. Some precautions on how to avoid processing induced flaws in aluminum–alumina bulk composites and FGMs are mentioned.This review addresses potential flaws in metal ceramic interpenetrating phase composites (IPCs) and FGMs at different stages of their manufacturing processes. For aluminum–alumina IPCs the impact of process parameters, selection of pore forming technique, pore network morphology and wettability of ceramic preform by molten metal are discussed. The paper helps identify potential risks when considering the infiltration route for Al/Al2O3 manufacturing.
      PubDate: 2017-08-01T09:22:58.595422-05:
      DOI: 10.1002/adem.201700484
       
  • Tensile and High-Cycle Fatigue Properties of Steel Sheet with Trace
           Silicon
    • Authors: Meng Xiao Zhang; Jian Chao Pang, Li Bei Zhu, Long Pan, Liang Liang Nie, Yun Xian Mao, Man Chen, Zhe Feng Zhang
      Abstract: The tensile properties, high-cycle fatigue properties, fracture surface morphologies, corresponding damage mechanisms, and dislocation patterns of two steels with trace silicon, 550TG and SD320, are investigated. It is found that the SD320 has a higher tensile strength than 550TG, but lower plasticity. In general, some deep cracks appear along the direction of rolling in all the tensile specimens and the fatigue limit of SD320 is higher. In particular, the 550TG shows a continuously decreasing S–N characteristic without fatigue limit at the higher cycle region, which can be explained by their differences of dislocation morphologies. Furthermore, the tensile and fatigue damage mechanisms are deeply analyzed and discussed.Due to the different evolutions of dislocations, there is a typical yielding plateau in 550TG and no similar phenomenon in SD320. Meanwhile, among the HCF region, the 550TG shows a continuously decreasing S–N characteristic; but for SD320, the knee point starts at 5 × 105 cycles. The fatigue limit is closely related to the yield strength.
      PubDate: 2017-07-28T06:16:04.263511-05:
      DOI: 10.1002/adem.201700476
       
  • Microstructure and Mechanical Properties of Al–12.6Si Eutectic Alloy
           Modified with Al–5Ti Master Alloy
    • Authors: Shuo Wang; Ya Liu, Haoping Peng, Xiaowang Lu, Jianhua Wang, Xuping Su
      Abstract: The Al–12.6Si eutectic alloy has been modified via the Al–5Ti master alloy to improve both microstructure and mechanical properties. The results show that the fraction of the primary α–Al phase in the Al–12.6Si alloy and the mechanical properties of the resulting alloy vary considerably after modification with the Al–5Ti master alloy at different temperatures. With increasing modification temperature, the fraction of primary α–Al in the Al–12.6Si alloy increases, varying with the amount of added Al–5Ti. For an added amount of 0.2 wt.% Al–5Ti, the fraction of primary α–Al in the Al–12.6Si alloy reaches a maximum. The tensile strength and elongation of an Al–12.6Si alloy modified with 0.2 wt.% Al–5Ti at different temperatures evidently increase compare with unmodified alloys.The eutectic point of Al–Si alloy moves to the right with increasing temperature, resulting in increase of the fraction of primary α–Al. Adding 0.2 wt.% Al–5Ti causes maximal moving distance of the eutectic point to the right, leading to the formation of maximal fraction of primary α–Al, and remarkable increase of mechanical properties of Al–12.6 wt.% Si alloy.
      PubDate: 2017-07-28T04:00:29.051838-05:
      DOI: 10.1002/adem.201700495
       
  • Compressive Response and Energy Absorption Characteristics of In-Situ
           Grown CNT-Reinforced Al Composite Foams
    • Authors: Xudong Yang; Kunming Yang, Jiwei Wang, Chunsheng Shi, Chunnian He, Jiajun Li, Naiqin Zhao
      Abstract: Carbon nanotube (CNT) reinforced Al composite foams with different CNT contents are fabricated through an improved powder metallurgy approach by combining in-situ chemical vapor deposition (CVD), short time ball-milling, and space-holder method. The CNTs are uniformly dispersed on the surface of Al particles by in-situ CVD process, followed by a short time ball-milling process enabling an excellent interfacial bonding between CNTs and the Al matrix. The pore size and microstructures of the composite foams can be well tailored by the carbamide particle templates. The yield strength and energy absorption capacity of composite foams reach 18.1 MPa and 15.8 MJ m−3 with 3.0 wt% CNT addition, which are ≈1.3 and ≈3.6 times higher than those of pure Al foam, respectively. The energy absorption efficiency of the CNT/Al composite foams achieves a maximum of ≈0.86, when the CNT content is up to 3.0 wt%. Additionally, compressive and energy absorption properties of the CNT/Al composite foams increase with the increment of relative density. The failure mode of the Al foam changes from plastic mode to brittle mode combined with ductile mode, as a result of CNT addition.Uniformly dispersed CNTs reinforced Al composite foams are successfully fabricated by the combination of an in-situ chemical vapor deposition, short-time ball-milling, and space-holder method. Besides, the pores well replicate the shape and size of the original spherical carbamide particles.
      PubDate: 2017-07-26T07:45:35.038967-05:
      DOI: 10.1002/adem.201700431
       
  • Non-Isothermal Simulations of Aluminum Depth Filtration
    • Authors: Cornelius Demuth; Eric Werzner, Miguel A. A. Mendes, Hartmut Krause, Dimosthenis Trimis, Subhashis Ray
      Abstract: The present article addresses the modeling issues, related to the numerical simulation of aluminum depth filtration inside a real filter section in presence of non-negligible temperature variation. The filter structure is obtained by digitizing the computed tomography (CT) scanned data of a characteristic ceramic foam filter. The modeling takes the process conditions of a filtration trial in a pilot casting line into account. The incompressible flow of liquid aluminum is solved by the lattice Boltzmann method (LBM) and the heat transfer is solved by the finite volume method (FVM). The temperature dependences of the viscosity and the density of liquid metal are specifically considered. Although the consideration of buoyancy force significantly affects the fluid flow, the temperature-dependent viscosity plays only a minor role. A Lagrangian tracking of particles is performed for modeling the filtration of inclusions. In accordance with the depth filtration theory, the computational results confirm an exponential decrease in the particle concentration with the filter depth. The overall filtration efficiency is found to remain almost unaffected by both buoyancy and temperature-dependent viscosity. Using the numerically determined filtration coefficient, the filtration efficiency is extrapolated for a real filter of larger length, although the experimental data are underpredicted.This article concerns the numerical modeling of aluminum depth filtration in consideration of temperature variations. In particular, the effects of temperature-dependent density and viscosity of the melt on the flow, heat transfer, and the filtration of nonmetallic inclusions are investigated. The predictions are compared with the filtration efficiency measured during a filtration trial in a pilot casting line.
      PubDate: 2017-07-26T07:40:47.235094-05:
      DOI: 10.1002/adem.201700238
       
  • Microstructural and Crystallographic Insights in a Martensite/Austenite
           Dual Phase Ni–Mn–Sb Alloy
    • Authors: Chunyang Zhang; Haile Yan, Yudong Zhang, Claude Esling, Xiang Zhao, Liang Zuo
      Abstract: For Ni–Mn–Sb multifunctional alloy, its microstructure and crystallographic information are decisive factors for its multiple magnetic field induced properties, such as magnetic field induced shape memory effect, magneto-caloric effect, exchange bias effect, and so on. While, studies on such field are rarely conducted. In the present work, a thorough study on microstructural features and crystallographic characteristics has been conducted in a martensite/austenite dual phase coexisting polycrystalline Ni50Mn37Sb13 alloy. Results show that the martensite is self-organized in plates in the original austenite. The intra-plate martensite presents a fine lamellar microstructure and each fine lamella corresponds to one martensite variant. Crystallographic orientation analysis indicates that each martensite plate exists four differently oriented martensite variants and they can form three types of twins, type I, type II, and compound twin. Trace analysis results show that the interface between adjacent variants are their twinning plane K1. Further investigation on martensitic transformation orientation relationship reveals that the Pitsch orientation relationship, specified as {01¯1¯}A//{22¯1¯}Mand A//M, is the effective one from austenite to martensite. All the above results offer basic microstructural and crystallographic information on Ni–Mn–Sb alloys and can be useful for further investigation on property optimization of these alloys.Ni–Mn–Sb alloys are promising multi-functional materials owing to their various magnetic properties, which are closely associated with the crystal structure, microstructure, crystallographic features of martensite, and the martensitic transformation. In the present work, a comprehensive study has been conducted on microstructural and crystallographic characteristics of martensite and martensitic transformation orientation relationship in Ni–Mn–Sb alloys.
      PubDate: 2017-07-25T06:30:45.105149-05:
      DOI: 10.1002/adem.201700221
       
  • Texture, Microstructure, and Surface Mechanical Properties of AZ31
           Magnesium Alloys Processed by ECASD
    • Authors: Emigdio Mendoza Fandiño; Raúl E. Bolmaro, Pablo Risso, Vanina Tartalini, Patricia Fernández Morales, Martina Ávalos
      Abstract: The current work presents the results on Mg AZ31B alloy sheets subject to four passes using Equal Channel Angular Sheet Drawing (ECASD) at various temperatures (25, 100, and 200 °C). Textures are determined by laboratory X-ray diffraction and EBSD. EBSD allows the evaluation of the evolution of crystal sizes in function of the distance to the surface and the presence of twinning. Twinning is evident by the analysis of the textures, which show mainly two components, one due to the spin induced by the shearing of ECASD and the other one as a direct product of twinning. Micro-hardness, by Knoop tests on the lateral face of the sheets, are performed, allowing the determination of the influence of SPD on the hardness from surface to surface, going through the center of the sheet. Almost 50% increase on hardening, with respect to the non-processed material, is obtained near to the surface after four and six passes. The effectiveness as a hardening technique declined after the first four passes.The textures of Mg AZ31B alloy sheets subject to Equal Channel Angular Sheet Drawing (ECASD) at various temperatures are measured by X-ray diffraction and EBSD. Figure shows twinning behavior (White lines) of the internal region of the sample subject to ECASD with 120o die at 100 oC.
      PubDate: 2017-07-24T07:40:55.018843-05:
      DOI: 10.1002/adem.201700228
       
  • Tailored Surface Properties of Ceramic Foams for Liquid Multiphase
           Reactions
    • Authors: Katja Schelm; Michael Schwidder, Janis Samuel, Franziska Scheffler, Michael Scheffler
      Abstract: Open cellular ceramic foams are prepared using the replica method. In a second step, these foams are coated with a pre-ceramic or polymer-derived ceramic coating, respectively. Polymer-to-ceramic transformation is studied by SEM with respect to the microstructure, functional groups are characterized by Raman microscopy, density and porosity are determined by pycnometer measurements as well as the surface free energy by means of contact angle measurements. By pyrolysis at different temperatures between 403 and 1273 K, the surface wettability is adjusted in a wide range from hydrophilic to hydrophobic due to the release of organic groups from the pre-ceramic polymers in terms of polymer-to-ceramic transformation. Coated foams are tested in a new potential application: as reactor internals to increase the liquid–liquid interface area in a homogeneously catalyzed multiphase system. As model reaction, a reactive extraction of an organic dye was used and the influence of the surface energy of the foam on the phase dispersion/reaction rate is discussed. The coated foams are able to increase the reaction rate to an extent depending on the surface wettability.Ceramic foams are prepared and coated with pre-ceramic polymers. These coating offers to tailor the surface properties like the wetting behavior in wide range by variation of the pyrolysis temperature. Due to the foams structure, they are useful for novel multi-phase mixing processes. This work shows the dependence of the phase dispersion of two immiscible liquid phases. This work shows the dependence of the phase dispersion of two immiscible liquid phases on the surface wettability of the foams.
      PubDate: 2017-07-21T06:45:28.600191-05:
      DOI: 10.1002/adem.201700418
       
  • Direct Liquid Injection − Low Pressure Chemical Vapor Deposition of
           Silica Thin Films from Di-t-butoxydiacetoxysilane
    • Authors: Mattias Vervaele; Bert De Roo, Jolien Debehets, Marilyne Sousa, Luman Zhang, Bart Van Bilzen, Stephanie Seré, Herve Guillon, Markku Rajala, Jin Won Seo, Jean-Pierre Locquet
      Abstract: In this work, an unusual silicon chemical vapor deposition precursor is used, which allows the safe deposition of thin silica films in a controlled and reproducible manner at a lower thermal budget with a newly developed direct liquid injection − low pressure chemical vapor deposition system. The deposition is controlled by parameters such as deposition temperature, partial pressure of the gases, and flow rate of the precursor solution. X-ray reflectivity and spectroscopic ellipsometry of the deposited samples show that the thickness of the layers is well controlled by deposition temperature, time, and oxygen flow. A growth rate of 4.5 Å min−1 is obtained without the addition of oxygen, which can be increased to 10.2 Å min−1 by the addition of oxygen. Atomic force microscopy, Rutherford backscattering spectroscopy, Fourier transform infrared spectroscopy, and drop shape analysis are used to measure roughness, composition, and hydrophobicity. Thin films of silicon dioxide are successfully grown. In addition, this newly developed system can be used for a wide range of films by varying the precursors or by co-injecting nanoparticles suspension mixed with the chemical vapor deposition precursor in the direct liquid injection vaporizer.This work describes the use of the unusual silicon chemical vapor deposition precursor di-t-butoxydiacetoxysilane (DADBS), which allows the safe deposition of thin silica films in a controlled and reproducible manner at a lower thermal budget with a newly developed direct liquid injection – low pressure chemical vapor deposition system.
      PubDate: 2017-07-17T04:11:31.246894-05:
      DOI: 10.1002/adem.201700425
       
  • Severe Plastic Deformation by Equal Channel Angular Pressing and Rolling:
           The Influence of the Deformation Path on Strain Distribution
    • Authors: Andrea M. Kliauga; Vitor L. Sordi, Natalia S. De Vincentis, Raúl E. Bolmaro, Norbert Schell, Heinz-Günter Brokmeier
      Abstract: The present work compares two deformation techniques, rolling and Equal Channel Angular pressing (ECAP), and the response offered by three different materials that differ in Stacking Fault Energy (SFE): AA1010 Al, commercially pure Cu, and an austenitic stainless steel. The objective of this investigation is to study the effect of each deformation mode on tensile behavior, deformation mechanism, texture, and microstructure and to establish the influence of the stacking fault energy on said effects. The results show that the different strain paths of ECAP and rolling do not affect the strength, but rolling leads to an accentuated texture and thus to elastic and plastic anisotropy. This finding has practical relevance for micro manufacturing techniques. Furthermore, it is observed that lower SFE results in smaller domain size and higher dislocation density, which are microstructural details related to strength and to the work hardening capacity. Finally, both techniques are able to produce a high amount of high angle grain boundaries, a feature that characterizes refined microstructures. These processes operate at different strain rates; thus, in low SFE materials, a more effective grain fragmentation by deformation-induced twins is observed after the ECAP process.Rolling and equal channel angular pressing (ECAP), and the response offered by three materials were compared. The different strain paths of ECAP and rolling do not affect the strength, but rolling leads to smaller domain sizes and an accentuated texture, which induces elastic and plastic anisotropy. These processes operate at different strain rates; thus, in low stacking fault energy (SFE) materials, a more effective grain fragmentation by deformation- induced twins is observed after the ECAP process.
      PubDate: 2017-07-14T00:34:41.114924-05:
      DOI: 10.1002/adem.201700055
       
  • Preparation of Ni-Encapsulated ZTA Particles as Precursors to Reinforce
           Iron-Based Composites
    • Authors: Juanjian Ru; Yehua Jiang, Rong Zhou, Jing Feng, Yixin Hua, Qionglian Yang
      Abstract: Ni-encapsulated ZTA (ZTA@Ni) particles as precursors to reinforce high chromium cast iron (HCCI) matrix composites are synthesized by electroless deposition using a choline chloride-ethylene glycol (ChCl-EG) ionic liquid additive. The effects of NiSO4 concentration, ChCl-EG concentration, reaction temperature, and ZTA loading capacity on the surface morphology, coating thickness, and elemental distribution of the ZTA@Ni particles are investigated. The deposition sequence of the Ni coating layer is analyzed according to changes in the morphology of samples obtained at different reaction stages. A schematic illustration of the deposition process with the ChCl-EG additive is established. It is demonstrated that ChCl-EG plays the important role of hindering the fast nucleation and crystal growth of Ni nuclei. In addition, the abrasive wear resistance of the ZTA@Ni-reinforced HCCI composite is higher than that of the matrix and the ZTA-reinforced composite. Close contact between the ZTA@Ni particles and the matrix benefits load transfer from the matrix to the reinforcement. The diffusion of metallic Ni leads to the formation of numerous nuclei to refine the particle size of carbides adjacent to the interface and reinforce the interfacial bonding strength.Ni-encapsulated ZTA particles as precursors to reinforce iron matrix composites are prepared by electroless deposition using a choline chloride-ethylene glycol (ChCl-EG) ionic liquid additive. The deposition sequence of the Ni coating layer is analyzed, and a schematic illustration is proposed. ChCl-EG plays the role of hindering the fast nucleation and crystal growth of Ni nuclei.
      PubDate: 2017-07-10T04:16:10.330658-05:
      DOI: 10.1002/adem.201700268
       
  • Carbon Coated Alumina Nanofiber Membranes for Selective Ion Transport
    • Authors: Vera S. Solodovnichenko; Denis V. Lebedev, Victoria V. Bykanova, Alexey V. Shiverskiy, Mikhail M. Simunin, Vladimir A. Parfenov, Ilya I. Ryzhkov
      Abstract: The authors propose a novel type of ion-selective membranes, which combine the advantages of ceramic nanofibrous media with good electrical conductivity. The membranes are produced from Nafen alumina nanofibers (diameter around 10 nm) by filtration of nanofiber suspension through a porous support followed by drying and sintering. Electrical conductivity is achieved by depositing a thin carbon layer on the nanofibers by chemical vapor deposition (CVD). Raman and FTIR spectroscopy, X-ray fluorescence analysis, and TEM are used to confirm the carbon structure formation. The deposition of carbon leads to decreasing porosity (from 75 to 62%) and specific surface area (from 146 to 107 m2 g−1) of membranes, while the pore size distribution maximum shifts from 28 to 16 nm. Measurements of membrane potential in an electrochemical cell show that the carbon coated membranes acquire high ionic selectivity (transference numbers 0.94 for anion and 0.06 for cation in aqueous KCl). Fitting the membrane potential data by the Teorell–Meyer–Sievers model shows that the fixed membrane charge increases proportionally with increasing electrolyte concentration. The carbon coated membranes are ideally polarizable for applied voltages from −0.5 to +0.8 V. The potential applications of produced membranes include nano- and ultrafiltration, separation of charged species, and switchable ion-transport selectivity.A novel type of ion-selective membranes based on alumina nanofibers with the diameter of ∼10 nm is proposed. A carbon layer deposited on the nanofibers by the CVD method provides electrical conductivity and ionic selectivity to the membranes. The potential applications of membranes include nano- and ultrafiltration of charged species. The nanofibrous structure with conductive carbon layer is perspective for realizing switchable ion-transport selectivity.
      PubDate: 2017-07-10T01:18:46.422282-05:
      DOI: 10.1002/adem.201700244
       
  • Composite Materials Based on Shape-Memory Ti2NiCu Alloy for Frontier
           Micro- and Nanomechanical Applications
    • Authors: Peter Lega; Victor Koledov, Andrey Orlov, Dmitry Kuchin, Aleksey Frolov, Vladimir Shavrov, Alexandra Martynova, Artemii Irzhak, Alexander Shelyakov, V. Sampath, Vladimir Khovaylo, Pnina Ari-Gur
      Abstract: Composite materials based on Ti2NiCu alloy, exhibiting shape memory effect (SME), have the unique capability of temperature-controlled reversible actuation on micro- and nanoscale. Three approaches to realizing this objective are demonstrated. The first one involves creating an amorphous-crystalline composite by passing accurately controlled electrical pulses through a rapidly-quenched amorphous Ti2NiCu ribbon. After undergoing partial crystallization (40–60% of crystalline phase), the composite acquires SME, and can be trained to undergo reversible deformations by a single bend in the martensitic condition. The second approach involves a layered composite consisting of a layer of Ti2NiCu and an elastic metallic layer, such as Pt. It is found that the reversible deformation of the Ti2NiCu/Pt composite created by FIB milling is>1%, when the thickness of SME layer is reduced from 1 μm to 100 nm. Further reduction (below 100 nm) results in smaller deformation. The third approach combines these two methods. A layer of crystalline Ti2NiCu is covered by a layer of the same alloy in the amorphous state using FIB. The authors believe that these composites, exhibiting SME, will trigger the fabrication of many novel devices and open up new opportunities in diverse areas of nanoscience and nanotechnology.This manuscript presents three approaches to realizing composite materials based on Ti2NiCu alloy, exhibiting shape memory effect for temperature-controlled reversible actuation on micro- and nanoscale. The authors believe that these composites will open up new opportunities in diverse areas of nanoscience and nanotechnology.
      PubDate: 2017-07-03T01:26:31.954358-05:
      DOI: 10.1002/adem.201700154
       
  • Ceramic Fibers Reinforced Functionally Graded Thermal Barrier Coatings
    • Authors: Chang Wang; Xiufang Cui, Guo Jin, Zonghong Gao, Jiannong Jin, Zhaobing Cai, Yongchao Fang
      Abstract: The long-term durability is a considerable challenge for the use of thermal barrier coatings (TBCs). In order to solve this problem, introduction of yttria-stabilized zirconia (YSZ) short fibers in functionally graded system is employed to strengthen the durability of TBCs. Four coatings are deposited on In738LC substrate by atmospheric plasma spray (APS). Thermal cycling behaviors and fiber toughening mechanisms of coatings are systematically studied. Result shows that the thermal cycling lifetime of graded TBCs with the addition of fibers can reach 406 ± 21 at 850 °C, which increases by 60% compared to that of typical APS YSZ TBCs. Moreover, the improvement of lifetime mainly attributes to the fiber breakage, the fiber-matrix interface debonding, and the crack deflection.In this study, a novel method, namely, introduction of yttria-stabilized zirconia (YSZ) short fibers in functionally graded system, is used to solve the long-term durability of TBCs. Thermal cycling lifetime of this TBC is improved greatly. The improvement is mainly attributed to the fiber breakage, the fiber-matrix interface debonding, and the crack deflection.
      PubDate: 2017-06-23T03:32:30.183391-05:
      DOI: 10.1002/adem.201700149
       
  • Life-Cycle Assessment of Solar Charger with Integrated Organic
           Photovoltaics
    • Authors: Gisele A. dos Reis Benatto; Nieves Espinosa, Frederik C. Krebs
      Abstract: Organic photovoltaics (OPV) applied in a commercial product comprising a solar charged power bank is subjected to a life cycle assessment (LCA) study. Regular power banks harvest electricity from the grid only. The solar power bank (called HeLi-on) is however, a power bank that includes a portable OPV panel, enabling the possibility to be charged from the sun, and not only from the grid. In this paper, two well-established power bank products using amorphous silicon solar panels (a-Si PV) and a regular power bank without any portable solar panel is compared to HeLi-on. The environmental impact of the products is quantified with the aim of indicate where eco-design improvements would make a difference and to point out performance of a portable solar panel depending on the context of use (Denmark and China), realistic disposal scenarios and the recycling relevance particularly concerning metals content.Ecodesign of electronic equipment as a key action supporting circular economy, reduce the energy consumption and other environmental impacts occurring throughout their life cycle. In this study, a new organic photovoltaic-based solar charger produced according to circular economy principles, is compared to well-established products in terms of environmental performance when used and disposed in Denmark or China, indicating ecodesign improvements.
      PubDate: 2017-06-16T07:56:03.278672-05:
      DOI: 10.1002/adem.201700124
       
  • Densification and Crystallization in Fe–Based Bulk Amorphous Alloy Spark
           Plasma Sintered in the Supercooled Liquid Region 
    • Authors: Tanaji Paul; Ashish Singh, Sandip P. Harimkar
      Abstract: Spark plasma sintering of Fe48Cr15Mo14Y2C15B6 bulk amorphous alloy at a range of temperatures in the supercooled liquid region (SLR) and above yielded near fully dense compacts. Upon sintering in the temperature range of 570–630 °C in SLR, large increments in density are observed due to enhanced sintering resulting from drastic reduction in the viscosity of the alloy. Above 630 °C, the absence of sufficient driving force for sintering and stiffening of the amorphous matrix from partial crystallization leads to sluggish densification. Analysis of the temperature profile in the sample and the die reveals that the temperature at the center of the sample is higher than that at the inner wall of the die as recorded by the thermocouple and the difference between the two is estimated to be between 31 and 53 °C.Spark plasma sintering of Fe48Cr15Mo14Y2C15B6 bulk amorphous alloy in the supercooled liquid region and above results in large densification upto 630 °C, due to reduction in viscosity and sluggish thereafter upto 800 °C due to (Fe,Cr)23(C,B)6 nanocrystallization induced matrix stiffening. The difference between the temperature at the center of the sample and that measured by the thermocouple is 31–53 °C.
      PubDate: 2017-06-16T01:00:22.596788-05:
      DOI: 10.1002/adem.201700224
       
  • Mechanical Behavior and Adhesion of the Ti/Cr/Au Metallization Scheme on
           Diamond Substrate
    • Authors: Sabeur Msolli; Joel Alexis, Heungsoo Kim
      Abstract: The mechanical properties of a Ti/Cr/Au metallization system deposited on a heavily doped diamond substrate are evaluated, first using nano-indentation tests. Various kinds of conditions are adopted, such as small and high force loadings. These tests are completed by in situ scanning electron microscopy observations of the surface. The adhesion of such multilayer on the diamond substrate is assessed using nano-scratching tests. The profiles of the obtained scratches are analyzed to detect any singularities or defects. Finally, a cross-section topography is performed, in order to obtain the cross profile of the scratch, and to determine the scratch hardness parameter of the metallization system. The Ti/Cr/Au metallization system is a potential candidate to play the role of ohmic contact on diamond. Therefore, its adhesion to diamond is important, since the whole power electronic assembly is mainly subjected to thermal cycling during service. The metallization system must adhere well to diamond, so as to resist temperature gradients and thermal strains that are widely observed in extreme thermal conditions. Otherwise, debonding phenomena may occur, and the whole electronic packaging fail.After the deposition of Ti/Cr/Au metallization system on diamond, microstructural analyzes of the deposit using SEM observations, EDX analysis, and EDS mapping show no viewable defects on the deposit surface. Nano-indentation tests prove that the deposit has a good mechanical behavior under mechanical loading. Finally, nano-scratching tests attest of the good adhesion of the deposit on diamond.
      PubDate: 2017-06-14T15:32:00.481262-05:
      DOI: 10.1002/adem.201700109
       
  • Toward Functionally Graded Polymer Foams Using Microfluidics
    • Authors: Jonas Elsing; Aggeliki Quell, Cosima Stubenrauch
      Abstract: Functionally graded polymer foams are of great interest for safety components or interfacial tissue engineering. However, most production methods lack control of the pore size. With the microfluidic technique we are able to introduce a defined pore size gradient in polymer foams using foamed emulsions and emulsions, respectively, as templates.Polymer foams with a defined gradient in pore size and density can be produced using microfluidics. For this purpose, the production parameters of the liquid templates, such as liquid flow rate or gas pressure are varied with time. The graded liquid template can then be polymerized.
      PubDate: 2017-06-07T04:55:31.7294-05:00
      DOI: 10.1002/adem.201700195
       
  • Influence of Mesostructure on Mechanical Property of Laminated Ti–Al
           Composites 
    • Authors: Shaoyuan Lyu; Yanbo Sun, Lei Ren, Wenlong Xiao, Chaoli Ma
      Abstract: Laminated Ti–Al composite sheets with different mesostructures have been fabricated through hot pressing. The influence of mesostructure on mechanical properties of the composite is investigated. The results indicate that with the increase of sintering temperature, different mesostructures of composite are obtained, that is, laminated Ti/Ti–Al composite, laminated Ti3Al/TiAl composite, and monolithic Ti3Al/TiAl composite. The mechanical properties tests reveal that laminated Ti/Ti–Al composite exhibits better comprehensive mechanical properties, including flexural strength, fracture toughness, and microhardness, than those of laminated Ti3Al/TiAl composite and monolithic Ti3Al/TiAl composite. The fracture analysis shows that the propagation route of crack is zigzag for Ti/Ti–Al composite, curving for laminated Ti3Al/TiAl composite, and approximately a straight line for monolithic Ti3Al/TiAl composite. The relevant strengthening and toughening mechanism of the composites is discussed.Incorporating one ductile layer into the brittle Ti–Al composite is a potential way to overcome low ductility and fracture toughness at room temperature. By controlling the mesostructures of the composite, three types of composites are obtained, among which, laminated Ti/Ti–Al composite exhibits better comprehensive mechanical properties than those of laminated Ti–Al composite and monolithic Ti–Al composite.
      PubDate: 2017-05-29T04:31:28.19734-05:0
      DOI: 10.1002/adem.201700070
       
  • Identifying the Stages during Ultrasonic Processing that Reduce the Grain
           Size of Aluminum with Added Al3Ti1B Master Alloy 
    • Authors: Gui Wang; Matthew S. Dargusch, Dmitry G. Eskin, David H. StJohn
      Abstract: The combined application of UST and Al3Ti1B grain refiner changes the macrostructure of untreated commercial purity aluminum from large millimeter sized columnar grains to equiaxed grains of a few hundred microns. This research reveals three distinct stages that affect the grain size, while UST is applied during melting and solidification. Stage I applied well above the liquidus temperature improves the efficiency of the refiner, possibly by de-agglomeration and wetting of TiB2 particles, and their distribution throughout the melt by acoustic streaming. Stage I is followed by Stage II, where little further improvement occurs. Stage III causes additional grain refinement when applied at and below the liquidus temperature, where nucleation of grains maybe enhanced by cavitation, which can also facilitate fragmentation and detachment of grains formed on the sonotrode. Convection due to acoustic streaming creates a uniformly undercooled temperature in the melt, which ensures the survival of these new grains during transport, as well as assisting the transport of grains to produce a uniform fine grain size throughout the ingot.Termination of ultrasonic treatment of Al with Al3Ti1B master alloy addition at a range of temperatures reveals three stages affecting grain refinement. The grain density is increased by five to ten times during stages I and III, which are above and below the liquidus temperature, respectively. The grain size decreased from 278 to 115 microns after 110 s of treatment.
      PubDate: 2017-05-29T04:30:59.036537-05:
      DOI: 10.1002/adem.201700264
       
  • A Combinatorial Approach for Assessing the Magnetic Properties of High
           Entropy Alloys: Role of Cr in AlCoxCr1–xFeNi 
    • Authors: Tushar Borkar; Varun Chaudhary, Bharat Gwalani, Deep Choudhuri, Calvin V. Mikler, Vishal Soni, Talukder Alam, Raju V. Ramanujan, Rajarshi Banerjee
      Abstract: A combinatorial assessment of composition-microstructure-magnetic property relationships in magnetic high entropy AlCoxCr1-xFeNi alloy (0 ≤ x ≤ 1) system has been carried out using compositionally graded alloys fabricated via laser additive manufacturing. At one end, the AlCoFeNi composition (x = 1) consisted of equiaxed B2 grains, exhibiting very early stages of phase separation (only compositional partitioning) into Ni–Al rich and Fe–Co rich regions within grains of the B2 phase. At the other extreme, the AlCrFeNi composition (x = 0) exhibited grains with pronounced spinodal decomposition, resulting in a B2 + bcc microstructure with the degree of spinodal decomposition progressively increasing with Cr content in these AlCoxCr1–xFeNi alloys. While the saturation magnetization (Ms) monotonically increases six times from x = 0 to x = 1, the coercivity (Hc) variation is non-monotonic, increasing seven times from x = 0 to x = 0.4, and subsequently decreasing fourteen times from x = 0.4 to x = 1.0. The magnetic phase transition temperature (Tc) for these alloys also increases monotonically with increasing Co content with a second phase transition exhibited in a certain range of compositions between x = 0.6 to x = 0.8. Such substantial changes in the magnetization behavior and properties of magnetic high entropy systems opens possibilities of tuning these alloys for specific soft or hard magnetic component applications.Laser Engineered Net Shaping (LENS™) process is used for making a compositionally graded magnetic AlCoxCr1–xFeNi HEA (0 ≤ x ≤1). The size scale of phase separation wave, which is affected by the composition, critically affects the magnetic properties like saturation magnetization and coercivity.
      PubDate: 2017-05-24T06:05:39.449627-05:
      DOI: 10.1002/adem.201700048
       
  • Size Effects in Continuous Drive Friction Welded Spray-Compacted
           Hypereutectic Al–Si Alloys 
    • Authors: Jian Feng; Marc Wettlaufer
      Abstract: Spray-compacted hypereutectic Al–Si alloy is one of the most important lightweight materials for casting components in electric vehicles. Size effects in such alloys jointed by continuous drive friction welding have been investigated by connecting the interfacial microstructure with the joint strength. The nature of phases present, the topology, and the dispersion of particles have been examined carefully. The mechanical properties of joints have been characterized by transverse tensile tests, microhardness tests, XRD residual stress measurements, and finite element simulations. Size effects on the strengthening of the joint strength and the fracture of particles have been evaluated qualitatively and quantitatively. It has been confirmed that the micromechanical strengthening, which is related to the average particle size d and proportional to d−0.5, and the residual stress together determine the joint strength. By means of the fracture-mechanical analysis, a lower and an upper limit of the particle size have been defined to assess whether a particle can be refined or not during continuous drive friction welding.Size effects in spray-compacted hypereutectic Al–Si alloys jointed by continuous drive friction welding have been investigated qualitatively and quantitatively by connecting the interfacial microstructure with the joint strength. The micromechanical strengthening, which is related to the average particle size d and proportional to d−0.5, and the residual stress evaluated by XRD residual stress measurements and finite element simulation, together determine the joint strength.
      PubDate: 2017-05-18T06:55:53.616329-05:
      DOI: 10.1002/adem.201700128
       
  • Fabrication of Copper Surfaces with Structures Mirroring Those of Wood via
           Electroplating and Their Hydrophobic Properties 
    • Authors: Tianchi Wang; Xu Feng, Jian Kong, Chingping Wong
      Abstract: Superhydrophobic metallic surfaces have a wide range of applications; therefore, their fabrication has drawn widespread attention. The cross-section of wood has a tubular porous structure and exhibits hydrophobic properties. In this study, inspired by the hydrophobic properties of wood, we electroplated copper on porous wood charcoal surfaces to obtain a superhydrophobic copper surface possessing a structure mirroring that of wood in areas in contact with the wood charcoal. This study used pinewood and Fraxinus mandschurica as templates, which are first sintered under oxygen-free conditions to obtain wood charcoal that retains the porous structure of wood. A thick layer of copper is then electroplated onto the surfaces of the porous carbon. After the copper layer is peeled off, it is found that the copper surface in contact with the porous carbon have formed a microstructure that is a mirror image of the natural structure of wood. This copper surface exhibited excellent levels of hydrophobicity after fluorosilane modification, with contact angles as high as 150°.Wood shows hydrophobic properties, which should be attributed to the porous structure of the wood. Inspired by wood, we electroplate copper on porous wood charcoal surface to obtain a copper surface possessing a structure mirroring that of wood. This mirror structure helps copper surface to obtain superhydrophobic property.
      PubDate: 2017-05-18T06:55:50.885917-05:
      DOI: 10.1002/adem.201700147
       
  • Simultaneous Fast Deformation and Solidification in Supercooled Liquid
           Gallium at Room Temperature 
    • Authors: Zhenwei W. Yu; Yuchen C. Chen, Frank F. Yun, Xiaolin L. Wang
      Abstract: The authors demonstrate that it is possible to transform a supercooled liquid metal at room temperature into a variety of shapes in solids by combined liquid metal deformation and induced crystallization from the supercooling state. The authors discover that both reversible deformation and irreversible deformation can be achieved simultaneously for supercooled liquid gallium in alkaline or acid electrolytes by using electrodes that are non-wetted or wetted with liquid gallium, respectively. Our findings on the simultaneous deformation and solidification offer a novel approach to controlled patterning and solidification of supercooled liquid gallium at room temperature.Controlling the shape of liquid metals is still a big challenge. Simultaneous deformation and solidification of supercooled liquid gallium is discovered by using an electric field in alkaline or acid electrolytes, which offer a novel approach to controlled patterning and solidification of supercooled liquid gallium at room temperature.
      PubDate: 2017-05-18T01:38:52.178836-05:
      DOI: 10.1002/adem.201700190
       
  • Highly Selective Adsorbent and Photacatalytic Material for Industrial
           Wastewater Treatment 
    • Authors: Vassilios Binas; Aggelos Philippidis, Apostolos Zachopoulos, George Kiriakidis
      Abstract: Advanced multifunctional sponge-type materials are obtained following chemical treatment of a Visible Light Photocatalyst (VLP) with an alkali aqueous solution under selected conditions. The resulting multifunctional material is fully characterized by XRD, SEM/EDX, TEM, FT-IR, RAMAN, and UV-Vis. It is found that the resulting material has high affinity to cationic dyes such as methylene blue (MB) and rhodamine 6G (Rh6G) and, thus may be employed as an environmental selective adsorbant for industrial wastewaters consisted of different mixtures of anionic and cationic dyes. On the other hand, this “sponge” like material if activated under visible light irradiation exhibits high photocatalytic activity for the decomposition of methylene blue in a solid state.The paper investigates an advanced multifunctional sponge type material suitable for novel membranes for industrial wastewater treatment, which could selectively adsorb pollutants and then recovery the clean membrane with exposure to visible light irradiation.
      PubDate: 2017-05-17T08:40:40.85499-05:0
      DOI: 10.1002/adem.201600661
       
  • Lamellar Ceramic Semicrystalline-Polymer Composite Fabricated by Freeze
           Casting 
    • Authors: Jiacheng Huang; Zhe Xu, Salvador Moreno, Seyedreza Morsali, Zhong Zhou, Soheil Daryadel, Mahmoud Baniasadi, Dong Qian, Majid Minary-Jolandan
      Abstract: Understanding the role of ductile polymer phase in mechanical behavior of bioinspired hybrid composites is an important step toward development of materials with damage tolerant properties. Herein, the authors report on fabrication and characterization of a bioinspired lamellar composite by incorporation of a semicrystalline polymer into a freeze casted scaffold. The elastic modulus and ductility of the polymer phase can be changed by more than three and 55 times, respectively, in addition to 42 folds decrease in modulus of toughness, by thermal annealing post-processing, after infiltration into the freeze casted ceramic scaffold. The results show that although polymer phase affects the fracture toughness and flexural behavior of the composite, the drastic changes in mechanical properties of the polymer phase has only marginal effect in the resulted properties of the composite. The authors use in situ SEM experiments and finite element simulation to investigate the deformation mechanism and the effect of the polymer phase on the distribution of stress in the fabricated composites.Directional freeze casting and vacuum infiltration is used to fabricate lamellar ceramic-polymer composites using ceramic micro-platelets and a semicrystalline polymer. Effect of thermal annealing on the morphology and properties of the polymer phase and its effect on mechanical properties of the fabricated composited is investigated.
      PubDate: 2017-05-15T11:50:45.997844-05:
      DOI: 10.1002/adem.201700214
       
  • Fatigue and Fracture Reliability of Shell-Mimetic PE/TiO2 Nanolayered
           Composites 
    • Authors: Y. J. Yang; B. Zhang, H. F. Tan, X. M. Luo, G. P. Zhang
      Abstract: Shell-mimetic (PE/TiO2)4 nanolayered composites stacked alternatively by 20 nm-thick PE layers and 55 nm-thick nanocrystalline TiO2 layers are synthesized by a combination of the layer-by-layer self-assembly and the chemical bath deposition methods. The critical cracking strain and the apparent fracture energy of the bio-mimetic nanolayered composites are determined as 0.56% and 0.98 J m−2, respectively, by the simply supported beam bending testing. Fatigue properties of the (PE/TiO2)4 nanolayered composites are evaluated by the dynamic bending testing method. The critical fatigue strain amplitude corresponding to the lowest strain amplitude for fatigue cracking of the present (PE/TiO2)4 NLCs is 0.0853%, which is much lower than the critical cracking strain (0.56%) under monotonic bending. The finding indicates that the potential fatigue threat to the long-term reliability of the bio-mimetic nanolayered composites needs to be concerned.Shell-mimetic (20 nm-PE/55 nm-TiO2)4 nanolayered composites are synthesized. The critical strain amplitude for cracking of the composites is 0.0853% under fatigue loading, being much lower than that (0.56%) under monotonic bending. The potential fatigue threat to the long-term reliability of the bio-mimetic nanolayered composites needs to be concerned.
      PubDate: 2017-05-15T01:40:51.431039-05:
      DOI: 10.1002/adem.201700246
       
  • Large Area One-Step Fabrication of Three-Level Multiple-Scaled Micro and
           Nanostructured Nickel Sleeves for Roll-to-Roll Hot Embossing 
    • Authors: Valentin Lang; Andreas Rank, Andrés F. Lasagni
      Abstract: Direct laser interference patterning enabled the fabrication of three level multiple-scaled microstructures on nickel surfaces using infrared picosecond laser pulses. While the largest spatial period (1.5 to 5.7 µm) could be controlled by adjusting the angle between the interfering laser beams and the laser wavelength, low and high spatial frequency laser induced periodic surface structures with pitches of approximately 800 nm and 160 nm, respectively, were also observed. Using a set of optimized processing parameters, large area Ni-sleeves were treated. These sleeves were later employed in preliminarily investigations of roll-to-roll high throughput hot-embossing of polymer foils.Direct Laser Interference Patterning is used to produce multiple-scaled microstructures on nickel surfaces using picosecond laser radiation. Using this method, structure depths up to 2 µm are achieved in a one-step process and even on the surface of large-area Ni-sleeves. Preliminary results on the use of the treated Ni-sleeves for roll-to-roll hot embossing processing are show for the first time.
      PubDate: 2017-05-12T08:47:42.578371-05:
      DOI: 10.1002/adem.201700126
       
  • A Novel Direct Liquid Injection Low Pressure Chemical Vapor Deposition
           System (DLI-LPCVD) for the Deposition of Thin Films 
    • Authors: Mattias Vervaele; Bert De Roo, Jolien Debehets, Marilyne Sousa, Luman Zhang, Bart Van Bilzen, Stephanie Seré, Herve Guillon, Markku Rajala, Jin Won Seo, Jean-Pierre Locquet
      Abstract: In this work, the use of a newly developed direct liquid injection low pressure chemical vapor deposition (DLI-LPCVD) system is described, which allows for the deposition of thin films in a controlled and reproducible manner. The capabilities of this system are described via silica thin films deposited using the precursor tetraethyl orthosilicate (TEOS). The deposition of thin films is controlled by parameters, such as deposition temperature, partial pressure of the gases, and flow rate of the precursor solution. The thickness of the deposited layer is varied simply by changing deposition temperature and time. X-ray reflectivity and spectroscopic ellipsometry of the deposited samples show that the thickness of the layers is well controlled by deposition temperature and time. Auger electron spectroscopy, in addition, motivates our choice to use cyclohexane as a solvent. A growth rate of 12.2 Å min−1 is obtained. Atomic force microscopy, Rutherford backscattering spectroscopy, Fourier transform infrared spectroscopy, and drop shape analysis are used to measure roughness, composition, and hydrophobicity. Thin films of silicon dioxide are successfully grown by the newly developed DLI-LPCVD system. This system can be used for a wide range of films by varying the precursors.This work describes the use of a newly developed direct liquid injection - low pressure chemical vapor deposition (DLI-LPCVD) system, which allows for the deposition of thin films in a controlled and reproducible manner. We describe the capabilities of this system via silica thin films deposited using the precursor tetraethyl orthosilicate (TEOS).
      PubDate: 2017-05-12T08:47:33.774192-05:
      DOI: 10.1002/adem.201700193
       
  • On the Breakdown of SiC during the Selective Laser Melting of Aluminum
           Matrix Composites 
    • Authors: Lachlan Connor Astfalck; Gemma Kaye Kelly, Xiaopeng Li, Timothy Barry Sercombe
      Abstract: Selective laser melting (SLM) is used to produce a SiC reinforced aluminum metal matrix composite (AMMC, Al–12Si plus 10 vol% SiC) with laser energy densities (Ep¯) between 20 and 80 J mm−3. Microstructural analysis shows that at lower energies, SiC is present in the Al–12Si matrix; however, at higher energies there is a distinct lack of SiC particles and the extensive formation of Al4C3 needles and primary Si particles. XRD analysis confirms a decrease in the volume of SiC and an increase in the amount of Al4C3 and primary Si with increasing Ep¯. This indicates that a reaction occurs between the Al and SiC during SLM. The underlying mechanism is attributed to the selective absorption of laser energy into the SiC particles, causing regions of extremely high temperatures. The formation of the reaction products cause errors in the theoretical density calculations. Therefore, X-ray micro tomography (XMT) is used to independently measure the relative density of the samples with a peak relative density ≈97.4%, which is much higher than that (relative density ≈93%) measured using the Archimedes method.Selective laser melting (SLM) is used to produce a SiC reinforced aluminum metal matrix composite. The content of SiC in the as-fabricated composites is influenced by the laser energy density. A reaction occurred between the Al and SiC during SLM due to extremely high local temperatures, which is attributed to the selective absorption of laser energy into the SiC particles.
      PubDate: 2017-05-11T03:16:12.679412-05:
      DOI: 10.1002/adem.201600835
       
  • Contribution of Ligand Oxidation Products to High Durability of Copper
           Films Prepared from Low-Sintering-Temperature Copper Ink on Polymer
           Substrates 
    • Authors: Yusuke Akiyama; Tomonori Sugiyama, Hideya Kawasaki
      Abstract: In electronic printing, ensuring high durability of sintered copper films on flexible substrates to obtain environmental stability and mechanical flexibility has become the most important task from a practical standpoint. In the study reported here, the authors develop solution synthesis of 2-amino-2-ethyl-1,3-propanediol (AEP)-protected copper nanoparticles (AEP–Cu NPs) with sizes of 3–8 nm in ethylene glycol, where the Cu NPs are stabilized via the metallacyclic coordination stability of the AEP ligands. The sintered Cu film exhibits a resistivity of 50 μΩ cm−1 after heating at 150 °C under a nitrogen atmosphere. Most importantly, the resulting Cu films on the polyethylene terephthalate (PET) substrates show excellent durability in terms of bending and adhesion without requiring any additives like nanotubes and nanowires. Furthermore, the authors successfully demonstrated the high environmental stability of the resulting Cu film even after it is exposed to harsh environmental conditions (RH 80%, 60 °C) for 1 month. The environmental durability is further improved by utilizing a composite ink of AEP–Cu NPs with copper microflakes. It is experimentally proven that oxidation products from AEP ligands originating in the sintering process contributed to the high durability of sintered copper films on flexible substrates.This study presents copper films prepared from copper ink with low sintering temperature on polymer substrates. They are highly durable in terms of bending and adhesion, without requiring any additives such as nanotubes and nanowires. Furthermore, the Cu film exhibits high environmental stability even after 1 month of storage under harsh environmental conditions (RH 80%, 60 °C).
      PubDate: 2017-05-10T06:10:45.638877-05:
      DOI: 10.1002/adem.201700259
       
  • Changing the Band Gaps by Controlling the Distribution of Initial Particle
           Size to Improve the Power Factor of N-Type Bi2Te3 Based Polycrystalline
           Bulks 
    • Authors: Chengcheng Zhang; Xi An Fan, Jie Hu, Chengpeng Jiang, Qiusheng Xiang, Guangqiang Li, Yawei Li, Zhu He
      Abstract: In this work, n-type Bi2Te2.7Se0.3 bulks are prepared by resistance pressure sintering technique from different particle sized powders, and the microstructure and electrical transport properties are investigated as function of the initial particle size distribution. With the initial particle size decreasing, more antisite defects, grain-boundaries and interface defects are introduced, and lead to a larger carrier concentration due to donor-like effect and a lower mobility due to the increasing grain boundary and carrier scattering, which results in a lower Seebeck coefficient and electrical resistivity. As a result, a maximum power factor of about 2.89 mW mK−2 at room temperature is achieved for the bulk sintered from the mix powders with different particle size distribution due to the optimization of the carrier concentration. The band gaps and the intrinsic excitation temperature are effectively adjusted by controlling the particle size in a narrow distribution. The sample sintered from the powders below 400 mesh has the highest average power factor above 2.44 mW mK−2 in the whole testing temperature range due to the improving band gaps and intrinsic excitation temperature.By controlling the particle size in a narrow range strictly, the carrier concentration and mobility are optimized. As a result, the average PF of about 2.44 mW mK−2 is achieved in the whole testing temperature range due to the improving band gaps and intrinsic excitation temperature.
      PubDate: 2017-05-10T06:10:32.884613-05:
      DOI: 10.1002/adem.201600696
       
  • Investigation on Behavior of Elastoplastic Deformation for
           Ti–48Al–2Cr–2Nb Alloy by Micro-Indentation and FEM-Reverse
           Algorithm 
    • Authors: Zhanwei Yuan; Chunwei Wang, Fuguo Li, Yongbiao Hu, Yajie Guo, Qi Chen, Yingying Wang, Mengle Guo
      Abstract: The Young's modulus, microhardness, and plastic properties of Ti–48Al–2Cr–2Nb alloy were determined using the micro-indentation technique. Oliver–Pharr method was used to calculate Young's modulus and microhardness. The indentation load was inversely correlated to Young's modulus and microhardness. The decreased Young's modulus was associated with indentation damage, while decreasing hardness was due to indentation size effect. The plastic properties were determined using proposed FEM-reverse algorithm, which combine finite element method and Matlab GA optimization tools. We used uniaxial compression test to verify the plastic properties calculated from the indentation tests, and it was found that the stress–strain plots predicted by FEM-reverse algorithm was quite similar to the test results.In this study, the mechanical properties of Ti–48Al–2Cr–2Nb are investigated by micro-indentation experiments. A FEM-reverse algorithm, which combined FEM simulation with Matlab GA optimization tools is proposed. And the FEM-reverse algorithm has been verified with good prediction.
      PubDate: 2017-04-27T18:57:57.723039-05:
      DOI: 10.1002/adem.201700097
       
  • Effect of Room and High Temperature Compaction on Optical and Mechanical
           Properties of HIPed Transparent Spinel Ceramics  
    • Authors: Papiya Biswas; Pandu Ramavath, Chandrashekhar Sadasiv Kumbhar, Dinesh S. Patil, Tapas Kumar Chongdar, Nitin Madhusudan Gokhale, Roy Johnson, Mantravadi Krishna Mohan
      Abstract: Spinel specimens are processed through Hot Pressing at 1620 °C and 20 MPa (designated as HPS) and uniaxial pressing at room temperature with 80 MPa followed by pressure-less sintering at 1650 °C (designated as CS). HPS exhibit translucency with marginally higher density (99.8% of theoretical density (TD)) in comparison to CS with 99.5% of TD and negligible transmission value. HPS samples have shown a transmission of 40 and 76% in visible and midwave infrared (MWIR) region, respectively. Both HPS and CS samples are further subjected to Hot Isostatic Pressing (designated as HPS + HIP and CS + HIP, respectively), at identical conditions of 1800 °C and 195 MPa to achieve close to TD and transparency. HPS + HIP and CS + HIP samples enhance their transmission to 78 and 71% in visible region and 86 and 79% in MWIR region, respectively. Although most important parameter for transparent ceramics, i.e., transmission values are relatively high for HPS + HIP samples and exhibit substantially lower hardness and flexural strength values in comparison to CS + HIP samples at room and elevated temperature. Fractographic studies of samples fail under flexure at room and elevated temperature have exhibited cleavage fracture with longer facet length for HPS + HIP correlating well with microstructure. Difference in mechanical properties can be attributed to differences in grain size produced by two methodologies.MgAl2O4 spinel powder compacted under room and elevated temperature, are subjected to hot isostatic pressing followed by property evaluations. Though the samples, processed through both the routes have identical densities, mechanical properties are superior for cold compacted samples in comparison to hot compacted samples which have exhibits better optical transmission. Results are also correlated with processing conditions.
      PubDate: 2017-04-26T06:16:00.729072-05:
      DOI: 10.1002/adem.201700111
       
  • Ultrasonic Spot Welding of Nickel Foam Sheet and Aluminum Solid
           Sheet  
    • Authors: Yan Xie; Mengnan Feng, Yangchuan Cai, Zhen Luo
      Abstract: Nickel foam sheet composed of three-dimensional (3D) triangular struts and aluminum solid sheet are welded via ultrasonic spot welding. The foam underwent acceptable thickness reduction and deformation, whereas most of the porous structures remain intact. Energy dispersive spectroscopy (EDS) analysis shows that little interdiffusion is noticed across the welding interface, leading to the formation of only a small amount of solid solution, and intermetallic compounds. Infrared temperature measurements show that the joint-temperature variation of the welding interface is substantially lower than the solid-solution temperature of Al/Ni, and the welding process is in solid state. The resistance of the joints is measured, and the contact resistance is calculated. The specimen with excellent interface connection exhibits low contact resistance. As the welding energy increases, the failure mode transitions from interfacial fracture to pull-out fracture, with the tensile load and fracture energy reaching 58 and 69%, respectively, of those corresponding to the nickel foam base metal. Fracture occurs exclusively on the nickel foam sheet, and the fracture mode is ductile fracture.Nickel foam sheet and aluminum solid sheet for battery tab and catalyst support are successfully joined via ultrasonic spot welding. The foam undergoes acceptable thickness reduction and deformation, whereas most of the porous structures remain intact. The mechanical and electrical properties of joints welded at different energies are studied. The welding process is in solid state.
      PubDate: 2017-04-26T06:10:34.310364-05:
      DOI: 10.1002/adem.201700094
       
  • Phase Stability of a Mechanically Alloyed CoCrCuFeNi High Entropy
           Alloy 
    • Authors: Shanmugasundaram Thangaraju; Thangaraju Emmanuel . Bouzy, Alain Hazotte
      Abstract: A CoCrCuFeNi high entropy alloy (HEA) is prepared from the high purity elemental Co,Cr, Cu,Fe, and Ni powders by mechanical alloying (MA) at different milling speed (200 or 350 rpm). Mechanically alloyed powder samples are subsequently annealed at different temperatures (300, 500, 700, and 800 °C). Microstructures, chemical composition, and phase stability of the powders are studied using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and energy dispersive X-ray spectrometry (EDS). The results show that, a single phase stable FCC solid solution is formed within 5 and 50 h of milling at 350 and 200 rpm, respectively. The single FCC phase is identified to be thermally stable upto 800 °C and then it is decomposed into two FCC phases. The second FCC phase is found to be rich in Cu. The precipitation of the Cu rich phase is likely due to the positive enthalpy of mixing of Cu with other alloying elements.Phase stability of a mechanically alloyed CoCrCuFeNi high entropy alloy is studied. A single phase FCC solid solution that formed within 5 h of alloying is retained upto 800 °C. Therefore, CoCrCuFeNi HEAs shall be heat treated or sintered below 800 °C to retain the single phase structure.
      PubDate: 2017-04-24T06:11:27.466596-05:
      DOI: 10.1002/adem.201700095
       
  • Stabilization of 2D Water Films in Porous Triple-Layer Membranes with a
           Hydrophilic Core: Cooling Textiles and Passive Evaporative Room Climate
           Control 
    • Authors: Mario Stucki; Wendelin J. Stark
      Abstract: Cooling and climate control are among the largest energy consuming processes in the world. By introducing passive systems, the energy consumption can be shifted to more renewable sources like sunlight. Combining hydrophobic and hydrophilic polymeric matrices in fully porous flat sheet membranes affords a triple-layer construct able of laterally transport water without energy input, while cooling and wetting the surrounding air by evaporation. In three subsequent coating steps, the material is assembled, the pore-forming template is released, and the materials are tested on their behavior in a passive cooling application. The straightforward and simple way of combining polymers with opposing chemical properties in a fully porous manner offers a wide range of new applications.Combining hydrophobic and hydrophilic polymeric matrices in fully porous flat sheet membranes affords a triple-layer construct able of laterally transport water without energy input, while cooling, and wetting the surrounding air by evaporation. In three subsequent coating steps, the material is assembled, the pore-forming template is released, and the materials is tested on their behavior in a passive cooling application.
      PubDate: 2017-04-24T06:11:23.900902-05:
      DOI: 10.1002/adem.201700134
       
  • Extreme-Value Statistics Reveal Rare Failure-Critical Defects in Additive
           Manufacturing 
    • Authors: Brad L. Boyce; Bradley C. Salzbrenner, Jeffrey M. Rodelas, Laura P. Swiler, Jonathan D. Madison, Bradley H. Jared, Yu-Lin Shen
      Abstract: Additive manufacturing enables the rapid, cost effective production of customized structural components. To fully capitalize on the agility of additive manufacturing, it is necessary to develop complementary high-throughput materials evaluation techniques. In this study, over 1000 nominally identical tensile tests are used to explore the effect of process variability on the mechanical property distributions of a precipitation hardened stainless steel produced by a laser powder bed fusion process, also known as direct metal laser sintering or selective laser melting. With this large dataset, rare defects are revealed that affect only ≈2% of the population, stemming from a single build lot of material. The rare defects cause a substantial loss in ductility and are associated with an interconnected network of porosity. The adoption of streamlined test methods will be paramount to diagnosing and mitigating such dangerous anomalies in future structural components.Arrays of tensile bars printed by laser powder bed fusion (additive manufacturing) are tested with a high-throughput mechanical test method. The resulting property distributions reveal within- and between-build variability as well as anomalous behavior associated with rare, failure-critical defects.
      PubDate: 2017-04-21T06:45:54.645985-05:
      DOI: 10.1002/adem.201700102
       
  • Net Shape 3D Printed NdFeB Permanent Magnet 
    • Authors: Jaćim Jaćimović; Federico Binda, Lorenz G. Herrmann, Felix Greuter, Jessica Genta, Micha Calvo, Tomaž Tomše, Reinhard A. Simon
      Abstract: Three dimensional printing enables realization of complex shape rare earth permanent magnet that enable unlocking the full potential of electrical devices for energy consumption and renewable energy production.
      PubDate: 2017-04-21T03:36:30.3748-05:00
      DOI: 10.1002/adem.201700098
       
  • Direct Catalyst-Free Chemical Vapor Deposition of ZnO Nanowire Array UV
           Photodetectors with Enhanced Photoresponse Speed 
    • Authors: Zhaoyao Zhan; Liping Xu, Jianing An, Hejun Du, Zhankun Weng, Wenqiang Lu
      Abstract: ZnO-based photodetectors (PDs) have long response times at magnitude of tens to hundreds of seconds, hampering their practical UV detection. The slow oxygen chemisorption/desorption process is the main cause of the slow response of UV PDs based on single ZnO nanowires (NWs). Here, the authors find the response speed of ZnO NW-based UV PDs could be improved by directly fabricating UV PDs on entangled ZnO NW array grown on SiO2 through a catalyst-free chemical vapor deposition (CVD) process. Specifically, the interconnections in ZnO NW array creates NW–NW junction barriers, which dominate the inter-wire charge transport. The switching of UV illumination induces fast tuning of NW–NW junction barrier height, which contributes to the enhanced response speed of the ZnO NW array UV PDs.Carrier generation and transport in ZnO NW array PD. The extra Nanowire–Nanowire junction barriers dominate charge transport in the ZnO NW array; the electrons must overcome the junction barriers to transport from one NW to another. Under UV illumination, the height of junction barriers is much reduced, and thus conductivity of ZnO NW array is greatly enhanced.
      PubDate: 2017-04-20T05:02:10.054229-05:
      DOI: 10.1002/adem.201700101
       
  • On the Influence of Ta and Ti on Heat-Treatability and
           γ/γ’-Partitioning of High W Containing Re-Free Nickel-Based
           Superalloys 
    • Authors: Nils C. Ritter; Ekaterina Schesler, Alexander Müller, Ralf Rettig, Carolin Körner, Robert F. Singer
      Abstract: Refractory elements like W are potent solid solution strengtheners, but they are also heavy and costly. They should be used as sparingly as possible. In the present paper, a series of single crystal alloys are prepared with varying amounts of Ta and Ti, but constant overall refractory concentration and γ’-volume fraction. Partitioning behavior of W and other elements after solutionizing and ageing treatment is investigated. Both, Ta and Ti are able to increase the W content in the γ-matrix. This provides an effective strategy to maximize solid solution strengthening potential for a given overall W content of the alloy. The experimentally determined phase characteristics and homogenization behavior are compared with numerical simulation. Good agreement is observed.The investigation deals with the direct comparison of Ta and Ti as well as Ta + Ti combination regarding heat-treatability, transformation-temperatures, and their influence on the partitioning behavior of solid solution strengthening element W. Ta is more effective in pushing W from γ'-phase into matrix compared to Ti. In all three alloys every element except W can be homogenized completely.
      PubDate: 2017-04-19T06:12:56.661104-05:
      DOI: 10.1002/adem.201700150
       
  • Arbitrarily Shaped 2.5D Circuits using Stretchable Interconnects Embedded
           in Thermoplastic Polymers 
    • Authors: Bart Plovie; Yang Yang, Joren Guillaume, Sheila Dunphy, Kristof Dhaenens, Steven Van Put, Björn Vandecasteele, Thomas Vervust, Frederick Bossuyt, Jan Vanfleteren
      Abstract: A method to fabricate thermoplastically deformable electronic circuits is presented, with the intent of achieving low-cost 2.5D free-form rigid smart objects. This by utilizing existing flexible circuit technology based stretchable circuits, in combination with thermoplastic materials. After fabricating the circuit in a flat state, a thermoforming step shapes the device by heating it beyond its glass transition temperature, and pushing it against a mold. Preliminary tests show the feasibility to fabricate simple circuits using off-the-shelf circuit components; showing a minimal decrease in conductivity of the polyimide supported copper-based interconnects.An electronic device is fabricated in a flat state and deformed through a thermal process, after which it retains its shape. After analysis of existing technologies, their bottlenecks a novel method using existing flexible and stretchable circuit technology is proposed to achieve such devices. The feasibility is demonstrated using a series of demonstration devices.
      PubDate: 2017-04-18T02:45:32.975715-05:
      DOI: 10.1002/adem.201700032
       
  • Study of Interfacial Interactions in Physically Transient Soft Layered
           Structures: A Step toward Understanding Interfacial Bonding and Failure in
           Soft Degradable Structures 
    • Authors: Yuanfen Chen; Reihaneh Jamshidi, Wangyujue Hong, Nicole N. Hashemi, Reza Montazami
      Abstract: Soft multilayer structures have broad applications in transient electronics. Strain-mismatch-induced fracture is key in achieving physical transiency. Here, swelling-mismatch-induced fragmentation of physically transient electrodes is studied. The fragment size of the electrode layer as a function of initial defect distribution is investigated. The average fragment size is predicted and verified by a combination of experimental and FEM analysis. It is found that only large defects initiate fragmentation; this concept can be used to control disintegration of physically transient electronics by means of materials and design, and can be extended to study transiency of soft multilayer structures.Swelling-induced fragmentation of soft transient electrode and its dependency on the initial defect distribution are predicted by computational model and experimentally verified. Accumulation of swelling-induced stress facilitates crack initiation. Large defect initiate cracking earlier and merge small defect while propagating.
      PubDate: 2017-04-18T02:35:36.4696-05:00
      DOI: 10.1002/adem.201700139
       
  • Twist Extrusion as a Potent Tool for Obtaining Advanced Engineering
           Materials: A Review 
    • Authors: Yan Beygelzimer; Roman Kulagin, Yuri Estrin, Laszlo S. Toth, Hyoung Seop Kim, Marat I. Latypov
      Abstract: Twist extrusion (TE) is one of the most popular techniques of severe plastic deformation, aiming at imparting to a material a tailored microstructure and the associated property improvement. The article provides a survey of the literature on the mechanics of TE and the effect it has on the structure, texture, and the attendant properties of various materials, including metals and alloys, powder materials, and polymers. Special emphasis is placed on vortex flow during TE and its hitherto unexplored potential for producing micro- and macrostructures that promise superior properties of the materials. In particular, the possibility of creating novel hybrid materials with chiral inner architecture is demonstrated. The survey is concluded by a presentation of examples of practical applications of TE.Twist extrusion is a process producing large strains under high pressure that gives rise to vortex fluxes within the billet, as illustrated by the figure. The resulting transformation of its inner structure at various length scales – from nano to macro – can be used to create novel high-performance materials.
      PubDate: 2017-04-10T07:16:49.205257-05:
      DOI: 10.1002/adem.201600873
       
  • Fusion-Based Additive Manufacturing for Processing Aluminum Alloys:
           State-of-the-Art and Challenges
    • Authors: Anne I. Mertens; Jocelyn Delahaye, Jacqueline Lecomte-Beckers
      Abstract: The fusion-based additive manufacturing of Al alloys has been developing at an ever faster pace since early 2015, after a comparatively slow start with respect to other metallic materials. This paper reviews the recent developments with the aim of identifying challenges and opportunities for future work. Additive Al components possess strongly out-of-equilibrium microstructures resulting in potentially enhanced mechanical properties. A deeper understanding of the thermal history during fabrication, the design of new high strength alloys and the development of better adapted post-processing procedures are still needed to take full advantages of the specificities of additive manufacturing.The fusion-based additive manufacturing of Al alloys has been developing at an ever faster pace since early 2015, after a comparatively slow start with respect to other metallic materials. This paper reviews the recent developments with the aim of identifying challenges and opportunities for future work. Additive Al components possess strongly out-of-equilibrium microstructures resulting in potentially enhanced mechanical properties. A deeper understanding of the thermal history during fabrication, the design of new high strength alloys and the development of better adapted post-processing procedures are still needed.
      PubDate: 2017-04-06T08:16:34.62729-05:0
      DOI: 10.1002/adem.201700003
       
  • Stress and Induced Electric Polarization Modeling in Polar, Semi-polar,
           and Non-Polar AlGaN/GaN Heterostructures for Piezotronics Application 
    • Authors: Bartłomiej K. Paszkiewicz
      Abstract: Author developed a comprehensive model that allows analysis of polarization states inside AlGaN/GaN heterostructures with a special attention devoted to its applications in piezotronics field. The model enables prediction of polarization and stress states inside a heterostructure with arbitrary chosen Al content and of any crystallographic orientation. This is an issue of great importance for piezotronics devices development for both applications: sensor technology Strain Gated Transistors. In the model an approach focused on a layer matching process at nanoscale is applied. Thanks to this it is possible to describe polarization states in heterostructure in technology agnostic way. In this paper, method for predicting polarization states and stress states in AlGaN/GaN heterostructure is presented.This paper presents model that allows analysis of polarization states present inside AlGaN/GaN heterostructures with a special attention to its applications in piezotronics field. The model enables to predict a polarization and stress state inside a heterostructure with any Al content and of any crystallographic orientation. It is presented, that it is possible to control polarization state of heterostructure.
      PubDate: 2017-02-24T09:00:52.782795-05:
      DOI: 10.1002/adem.201600712
       
  • Simulation of Short Fatigue Crack Propagation in a 3D Experimental
           Microstructure 
    • Authors: Henry Proudhon; Jingyuan Li, Wolfgang Ludwig, Arjen Roos, Samuel Forest
      Abstract: A three dimensional simulation of short fatigue crack propagation in a polycrystalline microstructure using a crystal plasticity finite element model is carried out. The experimental microstructure which contains several hundreds grains, was obtained via diffraction contrast tomography. A step-by-step short fatigue crack growth model based on capturing the plastic activity at the crack tip is used. Technical details are given and discussed in light of the compromise needed to perform such demanding calculations. The crack propagates through several grains and depicts some of the characteristic short crack features observed experimentally in the literature.A simulation of short fatigue crack growth in an experimental three dimensional microstructure with several hundreds grains is carried out. To simulate the fatigue process in relation with the material crystallography, a crystal plasticity finite element model is used to capture the plastic activity at the crack tip. The crack propagates through several grains and depicts characteristic features previously observed experimentally.
      PubDate: 2017-02-06T03:01:11.654678-05:
      DOI: 10.1002/adem.201600721
       
  • Substrate Independent Elastic Modulus of Thin Low Dielectric Constant
           Materials
    • Authors: Oguzhan Orkut Okudur; Kris Vanstreels, Ingrid de Wolf, Ude Hangen, Anqi Qiu
      Abstract: The elastic modulus of a variety of porous low dielectric constant thin films with porosities in the range of 24–47% and thicknesses between 148 and 235 nm is calculated using the Oliver–Pharr method, an intrinsic thin film model based on the Li-Vlassak method, and finite element simulations in the elastic regime by taking the tip imperfections into account. It is shown that the substrate effects are significant even at shallow indentation depths and strongly depend on the nanoindenter geometry. Elastic modulus values extracted from the intrinsic thin film model and finite element simulations, although based on different approaches, are found to be very similar and independent of the nanoindenter geometry.Measuring the elastic modulus of thin films by nanoindentation technique is not a straightforward task due to the effect of the substrate. The magnitude of this effect depends on the indentation depth, indenter geometry, film thickness, and material properties of both the film and the substrate.
      PubDate: 2017-01-30T04:06:04.184667-05:
      DOI: 10.1002/adem.201600653
       
  • Advanced Raman Spectroscopy Using Nanofocusing of Light 
    • Authors: Thomas Nuytten; Janusz Bogdanowicz, Thomas Hantschel, Andreas Schulze, Paola Favia, Hugo Bender, Ingrid De Wolf, Wilfried Vandervorst
      Abstract: Raman spectroscopy is uniquely sensitive to crucial material properties like stress and composition, but is inherently diffraction-limited, impeding its application potential in nanostructured devices. Under correct polarization conditions, the Raman response from a periodic array of fins is dramatically enhanced inside the semiconductor material, re-enabling fast and non-destructive optical characterization of deep-subwavelength semiconductor patterns. In this paper, it is shown that the effect is not limited to the material system where it was first observed, and results of nanofocused Raman spectroscopy in a variety of semiconductor materials are presented. The authors illustrate and discuss how the universality of the enhancement creates a unique potential for non-invasive and rapid stress and composition measurements at the nanoscale.The dramatic enhancement of Raman scattering intensities from periodic arrays of narrow semiconductor fins is reported. For a variety of materials, nanofocusing of the incident light translates Raman spectroscopy into the nanoscale world. This, in turn, enables optical stress and composition metrology on deep-subwavelength semiconductor architectures.
      PubDate: 2017-01-13T02:55:43.441123-05:
      DOI: 10.1002/adem.201600612
       
  • The Challenge of Measuring Strain in FDSOI Device Structures – HRXRD as
           a Potential Method of Resolution 
    • Authors: Holm Geisler; Martin Weisheit, Petra Hofmann, Hans-Juergen Engelmann
      Abstract: The strain state of Si1-xGex/SiO2 dummy structures on FDSOI wafers is non-destructively characterized by HRXRD reciprocal space mapping. A transition from biaxial to uniaxial strain is detected on narrow condensed Si1-xGex lines with shallow trench isolation (STI), revealing an increasing in-plane elastic strain relaxation perpendicular to the trenches with decreasing line width, but no strain relaxation parallel to the trenches. The degree of crystallinity of Si1-xGex lines degrades with increasing annealing temperature and time. An additional elastic strain reduction appears in the direction parallel to the STI trenches after deposition of source-drain Si1-yGey islands between dummy gates. The separation of the Si1-xGex peaks from Si1-yGey remains unresolved if x and y are close to each other.On FDSOI wafers, the strain state of narrow c-Si1-xGex structures depends on the width wi of the active areas, as shown by HRXRD measurements. The original biaxial strain of the unstructured film converts more and more to a uniaxial strain along [110], whereas an elastic strain relaxation is observed along [−110] with decreasing wi. An additional change of the strain state of S/D-Si1-yGey islands on top of c-Si1-xGex structures is also observed along [110] for the narrowest gratings.
      PubDate: 2017-01-05T06:05:49.543944-05:
      DOI: 10.1002/adem.201600744
       
 
 
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