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COMPUTER SCIENCE (1153 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: 14)
Abakós     Open Access   (Followers: 3)
Academy of Information and Management Sciences Journal     Full-text available via subscription   (Followers: 68)
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: 12)
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: 9)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 4)
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: 54)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 10)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 25)
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: 2)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2)
Analog Integrated Circuits and Signal Processing     Hybrid Journal   (Followers: 5)
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: 4)
Archive of Numerical Software     Open Access  
Archives and Museum Informatics     Hybrid Journal   (Followers: 120)
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: 246)
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: 32)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 45)
British Journal of Educational Technology     Hybrid Journal   (Followers: 125)
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: 19)
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: 8)
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: 29)
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: 14)
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)

        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]
  • 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
    • 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
    • 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
    • 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
    • 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
  • Masthead: Adv. Eng. Mater. 7∕2017
    • PubDate: 2017-07-20T04:17:15.99274-05:0
      DOI: 10.1002/adem.201770023
  • Contents: Adv. Eng. Mater. 7∕2017
    • PubDate: 2017-07-20T04:17:11.97006-05:0
      DOI: 10.1002/adem.201770024
  • Front Cover: Advanced Engineering Materials 7∕2017
    • Abstract: The dynamic nucleation and evolution of α phase during hot deformation is totally different from heat treatment, as discussed in article number 1600859 by Jiangkun Fan and co-workers. The “necklace” microstructure forms and the Burgers orientation relationship between α/β is destroyed. The dynamic βα phase transformation and the dynamic recovery/recrystallization of β phase proceed simultaneously during the hot deformation. There is a competition mechanism between these two processes.
      PubDate: 2017-07-20T04:17:11.547426-05:
      DOI: 10.1002/adem.201770022
  • 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
  • Influence of Cell Size on Mechanical and Piezoelectric Properties of PZT
           and LNKN Ceramic Foams
    • Authors: Franziska Eichhorn; Jonas Biggemann, Simone Kellermann, Akinobu Kawai, Kensuke Kato, Kenichi Kakimoto, Tobias Fey
      Abstract: Piezoceramic foams made of lead zirconate titanate (PZT) and lithium sodium potassium niobate (LNKN-6) containing an open porosity>75 vol% are manufactured with varying cell size from 1369 to 265 μm and accordingly, strut size from 346 to 46 μm by replica method. Pore size distribution and strut thickness are determined by X-ray micro tomography investigations of PZT foams with 10, 30, 45, and 80 pores per inch (ppi). Fracture strengths σb between 0.29 and 1.52 MPa (PZT) and 0.04 and 0.07 MPa (LNKN-6) are determined by compression test and compared to Gibson and Ashby's model of open- and closed-cell foams and in dependence of the cell size. The longitudinal and transversal coupling coefficients d33 and d31 decrease in a range of 38 to 178 pCN−1 or −13 to −100 pCN−1 compare to dense reference material. In dependence of the cell size, the values of the coupling coefficients change about 79–93%. The relative permittivity decreases 93% by decreasing the cell size of the PZT and LNKN-6 foams.Piezoceramic foams of PZT and LNKN-6 (porosity>75 vol%) are manufactured by replica method. Depending on the cell size fracture strengths σb varied between 0.29 and 1.52 MPa (PZT) and 0.04 and 0.07 MPa (LNKN-6), as well the longitudinal and transversal coupling coefficients d33 and d31 decreased in a range of 38 to 178 pCN−1 or −13 to −100 pCN−1.
      PubDate: 2017-07-07T02:16:30.350748-05:
      DOI: 10.1002/adem.201700420
  • Tailoring the Microstructure and Mechanical Property of AZ80 Alloys by
           Multiple Twinning and Aging Precipitation
    • Authors: Chunpeng Wang; Renlong Xin, Dongrong Li, Bo Song, Zhe Liu, Qing Liu
      Abstract: AZ80 alloy is a relatively inexpensive age-hardenable Mg alloy. To improve its precipitation strengthening effect, the discontinuous precipitates generally nucleating from grain boundaries should be reduced. In this study, the authors applied strain-path change compression on a wrought AZ80 alloy to generate multiple {10-12} twins and then the pre-deformed alloy is subjected to aging at 180 °C for different period. The effects of the pre-generated twins on precipitation behavior and hence the mechanical properties are investigated. It is found that multiple {10-12} twins are formed in the AZ80 alloy after two paths of compressions along the transverse and rolling directions. Consequently, continuous precipitation is largely promoted during the subsequent aging process. Moreover, the continuous precipitates preferred to form inside the {10-12} twin lamellae. Discontinuous precipitation is almost inhibited during aging at 180 °C for 4–96 h in the sample containing many multiple twins. Compare to the directly peak-aged sample, the pre-twinned and subsequently peak-aged alloys generally exhibit greatly superior mechanical properties. The yield strength, ultimate strength, and elongation for tension along RD are 242 MPa, 476 MPa, and 19.4%, respectively. These excellent properties are attributed to the combined effects of grain refinement, texture weakening, and enhanced precipitate strengthening.Strain-path change compression is applied on a wrought AZ80 alloy to generate multiple {10-12} twins. During the subsequent aging process, continuous precipitation is largely promoted. Compare to the directly peak-aged sample, the pre-twinned and subsequently peak-aged alloys exhibit greatly superior mechanical properties. These excellent properties are attributed to the combined effects of grain refinement, texture weakening, and enhanced precipitate strengthening.
      PubDate: 2017-07-06T06:21:14.149532-05:
      DOI: 10.1002/adem.201700332
  • Crystallography of Martensitic Transformation in Epitaxial Ni50Mn30Ga20
           Thin Film
    • Authors: Bo Yang; Tingting Liu, Xiao Wen Hao, Zong Bin Li, Yu Dong Zhang, Gao Wu Qin, Marie-Jeanne Philippe, Claude Esling, Xiang Zhao, Liang Zuo
      Abstract: In the present work, scanning electron microscopy and electron backscatter diffraction technique revealed that the microstructure of epitaxial Ni50Mn30Ga20 thin films are composed of six different orientated NM martensite variant colonies. In each martensite variant colony, there are eight different orientated NM martensite variants. The six NM and 7M martensite variant colonies are transformed from six (101)A planes of austenite, with the transformation consequence from Austenite to 7M martensite and then to NM martensite. Cross section TEM examination reveals the coexistence of 7M martensite and NM martensite. The habit plane between 7M martensite and NM martensite can be determined as (001)mono of 7M martensite and (112)Tetr of NM martensite.EBSD characterization and crystallographic calculation indicates that the martensitic transformation sequence is from Austenite to 7M martensite and then to NM martensite (A  7M  NM) in the Ni50Mn30Ga20 thin films. Cross section TEM images presents the coexistence of 7M and NM martensite and the habit plane between the 7M and NM martensite.
      PubDate: 2017-07-06T06:20:54.167751-05:
      DOI: 10.1002/adem.201700171
  • Enhanced Bipolar Strain Response in Lithium/Niobium Co-Doped
           Sodium–Barium Bismuth Titanate Lead-Free Ceramics
    • Authors: Shang Gao; Zhaojun Yao, Li Ning, Guangzhi Dong, Huiqing Fan, Qiang Li
      Abstract: The (Na0.484Bi0.456Ba0.06)Ti0.97Nb0.03O3 − xLi+ (x = 0, 0.005, 0.01, 0.015) lead-free piezoelectric ceramics are prepared by conventional solid-state reaction technique. X-ray diffraction and surface scanning electron microscope images confirm the pure perovskite structure of sintered ceramics. Electric field and composition-dependent strain behavior are investigated. The highest bipolar strain of 0.47% is achieved at x = 0.01 with the applied electric-field of 70 kV cm−1, and the corresponding normalized strain (d33*) reaches up to 671 pm V−1. Moreover, the giant strain exhibits excellent thermal stability and fatigue-resistance (within 105 switching cycles) properties. The origin of the strain can be attributed to transition between ferroelectric and relaxor ferroelectric induced by the applied electric field, and introduction of Li cations further enhances the strain behavior. AC impedance analysis indicate the appearance of grain boundary effect with increasing Li+ addition, which is also reflected on the dielectric and dielectric loss curves. It is believed that the environmental friendly binary system can be a promising candidate for piezoactuators.In this work, Li/Nb co-doped Na0.484Bi0.456Ba0.06TiO3 ceramics are prepared using conventional solid-state reaction method. The giant electric-field-induced strain of 0.47% (E = 70 kV cm–1) is achieved, meanwhile, the strain exhibits excellent fatigue resistance and temperature stability properties. The Li/Nb modified lead-free polycrystalline ceramics can be a promising candidate for actuator applications.
      PubDate: 2017-07-06T06:20:28.580674-05:
      DOI: 10.1002/adem.201700125
  • Mass Transfer Performance of Porous Nickel Manufactured by Lost Carbonate
           Sintering Process
    • Authors: Pengcheng Zhu; Yuyuan Zhao
      Abstract: Open cell porous metals are excellent electrode materials due to their unique electrochemical properties. However, very little research has been conducted to date on the mass transport of porous metals manufactured by the space holder methods, which have distinctive porous structures. This paper measures the mass transfer coefficient of porous nickel manufactured by the Lost Carbonate Sintering process. For porous nickel samples with a porosity of 0.55–0.75 and a pore size of 250–1500 μm measured at an electrolyte flow velocity of 1–12 cm s−1, the mass transfer coefficient is in the range of 0.0007–0.014 cm s−1, which is up to seven times higher than that of a solid nickel plate electrode. The mass transfer coefficient increases with pore size but decreases with porosity. The porous nickel has Sherwood numbers considerably higher than the other nickel electrodes reported in the literature, due to its high real surface area and its tortuous porous structure, which promotes turbulent flow.Porous nickel manufactured by the Lost Carbonate Sintering (LCS) process has higher Sherwood numbers than many other nickel electrodes in the modest range of Reynolds number due to its high real surface area and tortuous structures.
      PubDate: 2017-07-05T04:31:56.334266-05:
      DOI: 10.1002/adem.201700392
  • Comparative Phenomenological Study of Fracture Behavior of Ceramic and
           Glass Foams under Compressive Stress Using In Situ X-Ray Microtomography
    • Authors: Jana Hubálková; Claudia Voigt, Anne Schmidt, Kirsten Moritz, Christos G. Aneziris
      Abstract: This contribution is dealing with the phenomenological characterization of the cracking and damage of two different brittle foam materials (ceramic foams and glass foams) under compressive load. The compression tests were performed in situ in X-ray microtomograph in order to visualize the formation of single crack and crack patterns in 3D. Successive microtomographic scans at different levels of compression strain provide an insight into the stressed microstructure of the ceramic and glass foams. The linked evaluation of the microtomographic scans and registered load-displacement curves clarify the different mechanical response of ceramic and glass foams. Both, ceramic and glass foams show in the early stages of load nearly elastic response. The compressive loading above the elastic region induces different behavior. Ceramic foams response with local failure of single struts and edges to increasing loading. In case of glass foams, the response is depending on whether the cells are predominantly open or close. Predominantly open cell glass foams features very brittle behavior whereas close cell glass foams show pseudo-ductile behavior with a formation of a crushing band transversal to the loading direction.This study is concerned with the phenomenological characterization of damage of two different brittle foam materials (ceramic and glass foams) under compressive load performed in situ in X-ray microtomograph. The linked evaluation of the microtomographic scans at different levels of compression strain and stress–strain curves clarify the different mechanical response of ceramic and glass foams. While the ceramic foams are subject of successive damage process, the response of glass foams is depending on whether the cells are open or close. Predominantly open cell glass foams features very brittle behavior with a shear deformation band whereas close cell glass foams show pseudo-ductile behavior involving the formation of a compaction deformation band perpendicular to the loading direction.
      PubDate: 2017-07-05T04:31:26.356567-05:
      DOI: 10.1002/adem.201700286
  • Simultaneous XEDS-EBSD Study of NiCoAlFeCu(Cr,Ti) Multi-Component Alloys
    • Authors: Francisco Cruz-Gandarilla; Oscar Coreño-Alonso, José Gerardo Cabañas–Moreno, Lisa H. Chan, Cynthia Gómez-Esparza, Roberto Martínez Sánchez
      Abstract: NiCoAlFeCu, NiCoAlFeCuCr, and NiCoAlFeCuCrTi high-entropy alloys are prepared by mechanical alloying and sintered at 1200 °C and a pressure of 1.5 GPa for 3 h. The alloys were characterized by X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and X-ray energy dispersive spectrometry (XEDS). The phases found are mostly variants of the face centered cubic (fcc) phases (space group Fm3¯m), bcc (space group Im3¯m), and hexagonal (space group P63/mmc). Adding Ti to the NiCoAlFeCuCr system has strong effects on the solubility of the elements in the different phases and increases dramatically the number of phases present. The use of EBSD and XEDS allowed identification of a cubic phase in NiCoAlFeCu samples, which cannot be identified by XRD alone, and confirmed its identification by XRD in NiCoAlFeCuCr samples. The spatial distribution of phases and the grain structure in the three different samples, measured by EBSD and XEDS, is reported.Phase analysis in NiCoAlFeCu HEA alloys by XRD is frequently complicated by the simultaneous occurrence of several simple fcc and bcc structures. By linking together EBSD and XEDS analysis, cubic phases with similar lattice parameters are differentiated and their microscopic spatial distribution is revealed.
      PubDate: 2017-07-05T04:31:13.915639-05:
      DOI: 10.1002/adem.201700215
  • Surface Functionalization of Micro/Nanostructured Titanium with Bioactive
           Ions to Regulate the Behaviors of Murine Osteoblasts
    • Authors: Guisen Wang; Yi Wan, Bing Ren, Teng Wang, Zhanqiang Liu
      Abstract: Surface topography and chemical composition are centrally important in current implants for enhancing cellular responses. To investigate the synergistic effect of micro/nanostructure and bioactive ions on the spreading, proliferation, and differentiation of murine osteoblasts, the micro/nanostructured titanium surface containing bioactive ions (Zn2+ and Sr2+) was fabricated via sandblasting, acid etching, alkali-heat treatment, and ion exchange. Compared to polished titanium substrates, micro/nanostructured titanium substrates displayed the enhanced roughness and hydrophilicity. And surface functionalization of micro/nanostructured using Zn2+/Sr2+ ions exhibited the sustained release for a period of time. Meanwhile, cell experiments indicated that the Zn/Sr loaded micro/nanostructured titanium surfaces had a great potential to promote cell spreading, proliferation, and differentiation. This study provides a more promising method to design the surface of titanium implants for enhancing osseointegration.The hierarchical micro/nanostructure containing bioactive ions (Zn2+ and Sr2+) were fabricated on the surface of titanium by combined use of sandblasting, acid etching, alkali-heat treatment and ion exchange. The treated titanium substrates presented sustained ion release behavior. Surface functionalization of micro/nanostructured titanium with bioactive ions provided a favorable interfacial environment for the spreading, proliferation, and differentiation of osteoblasts.
      PubDate: 2017-07-03T08:01:11.345968-05:
      DOI: 10.1002/adem.201700299
  • Numerical Modeling of Flow Conditions during Steel Filtration Experiments
    • Authors: Amjad Asad; Eric Werzner, Cornelius Demuth, Steffen Dudczig, Anne Schmidt, Subhashis Ray, Christos G. Aneziris, Rüdiger Schwarze
      Abstract: In the present article, the performance and the efficiency of ceramic filters for continuous steel filtration in an induction crucible furnace, which is part of the steel casting simulator facility located at Technische Universität Bergakademie Freiberg, is investigated numerically. In order to achieve this objective, a macro-scale simulation for the melt flow in the crucible is coupled with a pore-scale simulation for the flow inside the ceramic filter that is adequately resolved by its detailed filter geometry, obtained from computed tomography scan images. The considerable influence of the filter on the flow field is indicated from the present results. Moreover, the efficiency of the employed filter is also determined and compared for two pore densities.Numerical simulations are performed in order to determine the filtration efficiency of ceramic filters in an induction crucible furnace. Both pore-scale and macro-scale simulations are coupled in order to achieve this task. The considerable influence of the filter on the flow field is shown in the present article. Moreover, it is indicated that the filtration efficiency of the filters depends on the pore density of the filters.
      PubDate: 2017-07-03T07:07:30.137184-05:
      DOI: 10.1002/adem.201700085
  • 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
  • Application of X-Ray Microtomography to Evaluate Complex Microstructure
           and Predict the Lower Bound Fatigue Potential of Cast
           Al–7(0.7)Si–4Cu–3Ni–Mg Alloys
    • Authors: Thomas O. Mbuya; Ian Sinclair, Katherine A. Soady, Philippa A. S. Reed
      Abstract: The 3D architecture of intermetallics and porosity in two multicomponent cast Al–7(0.7)Si–4Cu–3Ni–Mg alloys is characterized using conventional microscopy and X-ray microtomography. The two alloys are found to contain intermetallic phases such as Al3Ni, Al3(NiCu)2, Al9FeNi, and Al5Cu2Mg8Si6 that have complex networked morphology in 3D. The results also show that HIPping does not significantly affect the volume fraction, size, and shape distribution of the intermetallic phases in both alloys. A novel technique similar to serial sectioning that circumvents quantification difficulties associated with interconnected particles is used to quantify the intermetallics. The largest particle size distribution is then correlated to fatigue performance using extreme value analysis to predict the maximum particle size in a sample of S-N fatigue specimens and subsequently, the lower bound fatigue life. The predictions are found to correlate well with fatigue data. The effect of HIPping on porosity characteristics is also characterized. Large pore clusters with complex morphology are observed in the unHIPped versions of both alloys, but more significant in the low Si (Al–0.7Si–4Cu–3Ni–Mg) alloy. However, these are significantly reduced after HIPping. The differences between 2D and 3D pore morphology and size distribution is discussed in terms of the appropriate pore size parameter for fatigue life prediction.Two cast Al–7(0.7)Si–4Cu–3Ni–Mg alloys contain a complex 3D network of intermetallics and large complex-shaped pores. HIPping reduces the volume fraction (Vf), size and shape complexity of pores, but no effect is observed for intermetallics except a slight reduction in the Vf of 0.7 wt% Si alloy. A novel technique akin to serial sectioning is used to quantify intermetallics. The upper tail of particle sizes correlates well with fatigue crack initiating particles.
      PubDate: 2017-07-03T01:26:19.534505-05:
      DOI: 10.1002/adem.201700218
  • 3D Printing of Free-Standing Stretchable Electrodes with Tunable Structure
           and Stretchability
    • Authors: Hong Wei; Kai Li, Wen Guang Liu, Hong Meng, Pei Xin Zhang, Chao Yi Yan
      Abstract: Free-standing stretchable electrodes with high stretchability and resistance stability are desired for future wearable electronic applications. However, it is very difficult to achieve high stretchability (typically restricted by the substrate) and meanwhile maintain low resistance change upon stretching. Innovative designs and fabrication strategies need to be developed to meet the required characteristics. We report the successful fabrication of free-standing wavy elastic electrodes achieving very high stretchability (>300% for PDMS) and outstanding resistance stability (only 5% relative resistance change at 100% strain), simultaneously. We systematically studied designs with different joining angles and shapes to optimize the electrode performances. The 3D free-standing electrodes with outstanding stretchability and electrical stability has great potential for further optimizations and applications in future stretchable and wearable electronic devices.We demonstrate the successful 3D printing of wavy elastic electrodes with high stretchability and excellent resistance stability. Stretchable electrodes with different shapes and designs were systematically studied. Serpentine shaped design with 45° joining angle exhibited the best performances, which is in contrary to conventional 2D electrodes. Our fabrication strategy paves the way for further 3D printing of more complex stretchable electronic devices.
      PubDate: 2017-07-03T01:25:27.849675-05:
      DOI: 10.1002/adem.201700341
  • Gradient Structures in Thin-Walled Metallic Tubes Produced by Continuous
           High Pressure Tube Shearing Process
    • Authors: Rimma Lapovok; Yuanshen Qi, Hoi P. Ng, Laszlo S. Toth, Yuri Estrin
      Abstract: A new severe plastic deformation process, the authors refer to as High Pressure Tube Shearing (HPTS), is proposed. This type of deformation processing enhances the strength of the walls of metallic tubes by producing gradient microstructures with ultrafine grained layers in near-surface regions. The thickness of the layers associated with a gradient in microstructure can be controlled by tuning the rotational and translational speeds of the process. The paper describes several examples of steel and titanium tubes processed by different variants of HPTS. The possibility of producing gradient microstructures with ultrafine grained layers at inner or outer surface of a tube, or at both surfaces is demonstrated by in-depth theoretical analysis, finite element simulations, and experimental investigation of the microstructure and texture of tube walls.A new continuous severe plastic deformation process, named High Pressure Tube Shearing, is proposed, Figure 1. This deformation technique enhances the strength of the walls of metallic tubes by producing gradient microstructures with ultrafine grained layers in near-surface regions. The thickness of the layers associated with a gradient in microstructure can be controlled by tuning the rotational and translational speeds.
      PubDate: 2017-07-03T01:21:52.402208-05:
      DOI: 10.1002/adem.201700345
  • Microstructure Evolution and Ablation Mechanism of C/C and C/C-SiC
           Composites Under a Hypersonic Flowing Propane Torch
    • Authors: Xiaochao Jin; Xueling Fan, Peng Jiang, Qiang Wang
      Abstract: The high-velocity oxygen fuel thermal spray system can provide a hypersonic flowing environment in which the temperature, pressure, and speed are all sufficiently high to represent a more realistic environment of hypersonic vehicles than that produced by traditional oxyacetylene flame. In this work, the ablation resistance of C/C and C/C-SiC composites under hypersonic flowing propane flame is investigated, and the microstructure evolution during the ablation process is examined. It is found that different ablation regions are formed depending on the size, and the distributions of temperature and pressure on the front surface of the samples. With the increase of ablation time, a dense and continuous oxide layer forms, which acts as a barrier to prevent the interaction of oxidizing gases and composites, and can also block the conducted heat and resist high temperature scouring of hypersonic flowing flame. In addition, a numerical analysis is performed using ANSYS Fluent software to investigate the fields of velocity, pressure, and temperature on the front surface and around the carbon fibers of the sample. The simulation results further demonstrate the evolution of microstructures of C/C and C/C-SiC composites.High-velocity oxygen fuel thermal spray system can provide a hypersonic flowing environment in which the temperature, pressure, and speed are all sufficiently high to represent a realistic environment of hypersonic vehicles. In this artical, experimental investigations are performed under hypersonic flowing propane torch to provide a better understanding of the ablation mechanism of ultra-high temperature ceramics modified C/C composites.
      PubDate: 2017-07-03T01:21:05.149151-05:
      DOI: 10.1002/adem.201700239
  • Rietveld Texture Analysis for Metals Having Hexagonal Close-Packed Phase
           by Using Time-of-Flight Neutron Diffraction at iMATERIA
    • Authors: Yusuke Onuki; Akinori Hoshikawa, Soichiro Nishino, Shigeo Sato, Toru Ishigaki
      Abstract: Texture is an important property especially for metallic materials having hexagonal close-packed crystal structure. In order to understand the overall property or change in the microstructure of materials, neutron diffraction is a powerful tool of investigation. In this study, we attempt to measure the textures of Ti­–6Al–­4V (mass%) alloy by using a time-of-flight neutron diffractometer, iMATERIA. The results indicate that the texture measurement for the hexagonal phase is possible with the same method as for cubic metals. The texture of cubic β phase, whose volume fraction is several percent, can simultaneously be determined together with the hexagonal α phase.Quantitative texture measurement/analysis for a HCP crystal is verified by using data from iMATERIA, time-of-flight-neutron diffractometer at J-PARC MLF, Japan. In the current study, textures of both HCP α and BCC β phases in Ti-6 mass% Al-4 mass% V are simultaneously determined by the Rietveld texture analysis using data acquired at a single neutron exposure.
      PubDate: 2017-07-03T01:20:47.925262-05:
      DOI: 10.1002/adem.201700227
  • Open-Porous Silicon Nitride-Based Ceramics in Tubular Geometry Obtained by
           Slip-Casting and Gelcasting
    • Authors: Dominik Brouczek; Thomas Konegger
      Abstract: Owing to its unique properties, silicon nitride is a frequently used materials choice in highly demanding applications in terms of thermal and mechanical load. In this work, porous silicon nitride-based support materials in hollow-tube configuration are generated through colloidal forming, and their respective properties for potential applications in the fields of membrane-based separation, filtration, or catalysis are evaluated. Shaping of the ceramics is achieved by two distinct casting techniques, slip-casting, and gelcasting, and the results of the respective methods are set in relation. Furthermore, a special focus is set on the correlation between sintering parameters and resulting porosity. Subsequently, air permeabilities of the generated structures are determined, illustrating a direct relation between processing parameters and resulting permeability. Darcian permeability values of up to 9 · 10−16 m2 are observed for samples exhibiting total porosities between 32 and 41 %. The findings allow for a predictability of suitable permeation properties for the structures’ anticipated application as complex-shaped non-oxide ceramic supports for membrane-based separation or catalysis, or as high-performance filter materials.Two distinct colloidal-based casting approaches (slip-casting and gelcasting) are evaluated for the generation of porous Si3N4 ceramics in tubular geometry, suitable for prospective applications in the fields of separation or catalysis. Partial sintering facilitates tightly controllable pore morphologies, thus allowing for a direct correlation between processing, porosity, and permeability characteristics of the tubular structures prepared.
      PubDate: 2017-07-03T01:20:37.057617-05:
      DOI: 10.1002/adem.201700434
  • A New Horizon for Barreling Compression Test: Exponential Profile Modeling
    • Authors: Mehdi Fardi; Ralph Abraham, Peter D Hodgson, Shahin Khoddam
      Abstract: Exponential Profile Model (EPM) has been recently proposed to interpret barreling compression test's (BCT) data. A basic solution of EPM enables estimation of friction factor and to calculate distributions of strain rate (and strain) in the sample. These critical pre-requisites allow to identify material's flow behavior and to indirectly measure static, dynamic, and meta-dynamic recrystallization properties of the material based on the behavior. In this work, EPM's basic solution is employed in a fixed friction factor mode, the model is assessed and its potentials are outlined. The assessment includes comparing EPM's sample solutions with two reference solutions. The references are a non-isothermal finite element model of BCT and the commonly used solution of the test; Cylindrical Profile Model (CPM). It is shown that despite variations of strain, strain rate, and temperature in Al1050 and AISI 304 stainless steel BCT samples, EPM's solutions agree reasonably well with the finite element solutions. This is particularly true for effective strains bellow 0.7 and friction factors bellow 0.2. It is concluded that EPM presented a far more reliable solution than CPM.A new analytical model for barreling compression test (Top) is introduced. The model (EPM), proves to be far more reliable than the existing models such as Cylindrical Profile Model. EPM relies on the initial and deformed geometry of the test sample (Top) and a new velocity filed (bottom) to identify the test's friction factor and its strain distribution.
      PubDate: 2017-06-29T07:26:25.153451-05:
      DOI: 10.1002/adem.201700328
  • Highly Conductive Three-Dimensional Printing With Low-Melting Metal Alloy
    • Authors: Kimball Andersen; Yue Dong, Woo Soo Kim
      Abstract: It has been challenging to develop a new functional material with high conductivity for the Fused Filament Fabrication (FFF) based 3D printing technology. The proposed low-melting metal alloy filament provides the key to overcome the challenges including printability and conductivity. For this report, two metal alloys are designed to evaluate their suitability for FFF. In order to achieve material compatibility of the designed filament material with the nozzle materials, different nozzle materials are also investigated using thermal analysis. Then, a custom extrusion nozzle is suggested using thermal modeling to optimize the melt-zone for reliable extrusion. And finally, 3D printed circuit is demonstrated from a 3D printed plastic case to the integrated printed-alloy connections for the light-emitting device.Highly conductive metal 3D printing is demonstrated with low-melting Tin-Bismuth-Silver alloy filaments for the integration of 3D printed electronics. The developed alloy filament demonstrates good extrusion characteristics due to its thixotropic nature. Co-deposition of the alloy into 3D printed PLA structures shows compatible with existing thermoplastic additive manufacturing systems.
      PubDate: 2017-06-28T08:05:56.978033-05:
      DOI: 10.1002/adem.201700301
  • Synthesis and Vacuum Cold Spray Deposition of Biofunctionalized
           Nanodiamond/Hydroxyapatite Nanocomposite for Biomedical Applications
    • Authors: Deyan Li; Xiuyong Chen, Yongfeng Gong, Botao Zhang, Yi Liu, Peipeng Jin, Hua Li
      Abstract: Insufficient biological performances of titanium alloys have been the long-standing problems for their clinical applications. Here, we report synthesis of novel hydroxyapatite/nanodiamond-bone morphogenetic protein 2 (HA-ND/BMP2) composite powder and their coatings deposited by vacuum cold spray operated at room temperature. The microstructure and chemistry of the HA-ND/BMP2 powder and coatings are characterized by transmission electron microscopy, field-emission scanning electron microscopy, thin-film X-ray diffraction, Raman spectrometry, and X-ray photoelectron spectroscopy. In vitro growth assay of osteoblasts on the coatings showed that the biofunctionalized nanodiamonds promoted cell adhesion and proliferation. This study provides a promising technical route for constructing biofunctionalized nanocomposites coatings for potential biomedical applications.Novel hydroxyapatite/nanodiamond-bone morphogenetic protein 2 (HA-ND/BMP2) coatings are fabricated on titanium substrates for biomedical applications by VCS processed at room temperature. The nanocomposite coatings offer significantly promoted biological properties for the titanium substrates by the presence of NDs and BMP2.
      PubDate: 2017-06-28T08:05:42.049826-05:
      DOI: 10.1002/adem.201700363
  • Phase-Control Enabled Superior Mechanical and Electrical Properties of
           Nanocrystalline Tungsten-Molybdenum Thin Films
    • Authors: G. Martinez; C. V. Ramana
      Abstract: The authors report on the design and stabilization of the mechanically hard and electrically resistive β-phase W-Mo nanocrystalline thin films at room-temperature (RT). The W-Mo films are deposited under different deposition temperatures in the range of Ts = RT–30 °C. Structural analyses indicate that, as deposited at RT, the W-Mo films crystallize in the metastable β-phase, while those deposited at higher Ts (100–300 °C) exhibit the thermodynamically stable α-phase. The phase-effect is significant on the mechanical characteristics; superior hardness (H); and modulus of elasticity (Er) are found in β-than in α-phase W-Mo films. At the β-to-α phase transformation, significant reduction occurs in H (40  25 GPa) and Er (275  225 GPa) coupled with a reduction in electrical-resistivity (320  180 µΩ-cm). Their findings and the phase-mechanical-electrical property correlation established may provide further possibilities to design and tailor the performance of W-based thin films for future electronic and electromechanical device applications.The authors report on the superior mechanical properties of nanocrystalline W-Mo thin films. The phase-effect is significant on the hardness and elastic modulus, which are high in β-than in α-phase W-Mo films. These findings and the phase-mechanical-electrical property correlation established may provide further possibilities to design and tailor the performance of W-based films for future electronic and electromechanical device applications.
      PubDate: 2017-06-28T08:05:29.719304-05:
      DOI: 10.1002/adem.201700354
  • 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
  • Hot Rectangular Extrusion Textures of Six Mg-Alloys Via Neutron
    • Authors: Heinz-Günter Brokmeier
      Abstract: Due to the high quality and statistics utilizing neutron diffraction for texture analyses, the crystallographic texture variation of six Mg-alloys is described in detail (AM20–AZ31–AZ61–AZ91–ZC71–WE43). More or less in all cases, the crystallographic texture is composed of some ideal texture components such as {0001} and {10–10} and fiber components such as  // ND and  // ED. There is a dependency of the existence and texture sharpness of texture components with alloying elements such as the amount of Al. ZC71 is special with one dominating texture component {10–10} . WE43 shows the split of the central pole in the basal pole figure but texture components are identical to other alloys without the tilt.Crystallographic texture of rectangular hot extruded Mg-alloys show a strong variation in texture type and texture sharpness. Examples show the (0002) and the (10–10) pole figures of Mg-AZ61 and MG-ZC71, first one with strong deformation texture and second one with strong recrystallization texture.
      PubDate: 2017-06-19T02:21:02.739758-05:
      DOI: 10.1002/adem.201700234
  • Improving Mechanical Properties of cp Titanium by Heat Treatment
    • Authors: Francis Wagner; Abdelouahab Ouarem, Thiebaud Richeton, Laszlo S. Toth
      Abstract: The yield stress and the ductility are very important mechanical quantities for materials selection. The paper deals with the question: how far is it possible to increase the yield stress without a significant loss of ductility by optimizing the final heat treatment in the elaboration stage. Commercially pure titanium sheets are subjected to different thermo-mechanical treatments to produce seven metallurgical states. The textures and the microstructures of the samples are studied by Electron Back Scattering Diffraction measurements, the mechanical behavior by tensile testing along the previous rolling, and the transverse directions of the sheet. The obtained microstructures display different grain sizes and varying fractions of recrystallized grains, together with slightly dissimilar textures. The yield stress increases with the decreasing grain size and obeys the classical Hall–Petch law. The grain size reduction results in a small decrease of ductility for extension along the rolling direction when the recrystallized volume fraction is higher than 80%. For extension along the transverse direction, however, the homogeneous deformation strongly decreases as soon as the material contains a small fraction of non-recrystallized grains. A good compromise between high yield stress and ductility is identified in a metallurgical state close to the end of primary recrystallization. This material state insures a relatively small grain size with all grains being in a recrystallized state.Mechanical properties are determined for cp titanium sheets after various heat treatments leading to different states (full or partial recrystallyzation). The YS increases without significant loss of ductility due to grain size and texture. Anisotropy is taken into account to define the best compromise.
      PubDate: 2017-06-19T02:20:42.877674-05:
      DOI: 10.1002/adem.201700237
  • Life-Cycle Assessment of Solar Charger with Integrated Organic
    • 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
  • Large-Scale Synthesis of Nanostructured Nitride Layer on Ti Plate Using
           Mechanical Shot Peening and Low-Temperature Nitriding
    • Authors: Quantong Yao; Jian Sun, Depeng Shen, Weiping Tong, Liang Zuo
      Abstract: A nanostructured nitride layer is produced on a large titanium plate using mechanical shot peening (MSP) followed by a low-temperature gaseous nitriding method. The combined effect of the MSP and low-temperature nitriding on the microstructural evolution and mechanical properties is investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, as well as hardness, wear resistance, and toughness tests. The results of the characterization are compared to a coarse-grained specimen produced by a standard nitriding process. The results show that a nitride layer with a thickness of 10–15 µm is produced on the MSP-treated Ti plate after nitriding at 550 °C for 5 h. The nitride layer is composed of nanostructured ϵ-TiN and γ-Ti2N phases with a high supersaturation of nitrogen. The nitriding kinetics is significantly enhanced by the nanocrystalline structure. The surface hardness, thickness of the hardened layer, and wear resistance of the nitrided MSP Ti plate are all enhanced relative to the coarse-grained nitrided sample. The toughness of the nanostructured nitrides is greatly improved compared with the conventional nitrided specimen.The authors firstly realize surface nanocrystallization technology in industrialization application. The gaseous nitriding can be performed on Ti plate at low nitriding temperature of 550 °C by nanocrystalline layer assistance. The nitrided layer thickness and toughness are significantly improved comparing with that of the coarse-grained nitrided specimen.
      PubDate: 2017-06-16T07:55:55.708924-05:
      DOI: 10.1002/adem.201700157
  • In Situ Study of Deformation Twinning and Detwinning in Helium Irradiated
           Small-Volume Copper
    • Authors: Wei-Zhong Han; Ming-Shuai Ding, R. Lakshmi Narayan, Zhi-Wei Shan
      Abstract: The influence of nanoscale helium bubbles on the deformation twinning and detwinning behavior of submicron-sized Cu is investigated under tension, compression, and cyclic loading. In situ nanomechanical tests performed inside a transmission electron microscope reveal that twinning and detwinning occur readily in helium irradiated copper under both tension and compression. Continuous shearing of helium bubbles by Shockley partials leads to twin formation, whereas the residual back-stress accumulated from dislocation-bubble interactions assist in detwinning. These interactions also elevate the critical shear stress for partial dislocation slip in helium irradiated Cu compared to that in fully dense Cu. The growth twin boundaries can significantly enhance the twinning stress in helium irradiated Cu pillar, and deformation twin-growth twin boundary interaction promotes the formation of internal crack and thus accelerates failure. The effect of crystallographic orientation and sample size on the overall deformation characteristics of helium irradiated Cu is briefly discussed. The current studies show that deformation twinning and detwinning are also active deformation models in helium irradiated small-volume copper.In situ nanomechanical tests performed inside a transmission electron microscope reveal that twinning and detwinning occur readily in helium irradiated copper under both tension and compression. Continuous shearing of helium bubbles by Shockley partials leads to twin formation whereas the residual back-stress accumulated from dislocation-bubble interactions assist in detwinning.
      PubDate: 2017-06-16T01:00:29.347648-05:
      DOI: 10.1002/adem.201700357
  • 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 (see figure).
      PubDate: 2017-06-14T15:32:00.481262-05:
      DOI: 10.1002/adem.201700109
  • Dynamic Corrosion and Material Characteristics of Mg–Zn–Zr Mini-Tubes:
           The Influence of Microstructures and Extrusion Parameters
    • Authors: Da-Jun Lin; Fei-Yi Hung, Heng-Jui Liu, Ming-Long Yeh
      Abstract: In this study, magnesium–zinc–zirconium (Mg–Zn–Zr) alloy mini-tubes that fit the diameter of cardiovascular stents are successfully fabricated using an isothermal extrusion method. The influence of extrusion temperature and ram speed on the microstructure are examined. In addition, this research develops a novel dynamic-corrosion apparatus for Mg alloy mini-tube examination, and supplemented with electrochemical, and biocompatibility tests, the optimal criteria for mini-tube extrusion are defined. The optimized specimen not only retains a homogeneous fine-grained structure with a grain size of about 2 µm, but also possesses 300 MPa yielding strength and nearly 15% elongation. Compared with a coarse-grained microstructure, the fine-grained specimens significantly reduces the corrosion and oxidation rates in a dynamic-flow field, resulting in favorable characteristics of degradation, cytocompatibility, and hemocompatibility. The results suggest that precisely controlling the extrusion process can improve the mechanical properties as well as the biocompatibility of Mg alloys for application in cardiovascular implants.The Mg mini-tube is developed for cardiovascular stent application. The extrusion parameter dominates the microstructure, which results in a significant increase in enhanced mechanical properties and corrosion resistance. A new dynamic corrosion test is performed in order to determine the practicability of fine-grained Mg mini-tube.
      PubDate: 2017-06-14T01:56:13.023829-05:
      DOI: 10.1002/adem.201700159
  • Microstructure and Corrosion Behavior of the Friction Stir Welded Joints
           Made from Ultrafine Grained Aluminum 
    • Authors: Marta Lipińska; Ewa Ura-Bińczyk, Lech Olejnik, Andrzej Rosochowski, Małgorzata Lewandowska
      Abstract: Joints made from ultrafine grained aluminium alloy 1050 are investigated in order to examine the corrosion behavior and microstructural changes between base materials and stir zones. Samples in the initial state, after four and eight passes of Incremental ECAP (I-ECAP) process were joined with similar plates using Friction Stir Welding. Initially refined microstructure after I-ECAP transformed to homogenous few micron sized grains structure in stir zones. AlFeSi particles present in the microstructure became fragmented during plastic deformation and welding process. The observed minor differences in corrosion resistance include slightly higher values of corrosion potentials but more complex pits’ morphology for I-ECAP processed samples comparing to the stir zones.The changes in the microstructure and corrosion resistance between base materials (BM) and stir zones (SZ) are investigated. The number refers to the number of I-ECAP passes of base material. After the corrosion tests, the surface of the samples was examined using SEM. With increasing number of I-ECAP passes, the pits pose more developed structure with linked cavities. For SZ samples, which exhibit higher grain size, the number of pits is reduced. Pits are also less developed but deeper. The number of pits and surface covered by them is connected with size of AlFeSi particles.
      PubDate: 2017-04-18T06:35:59.395926-05:
      DOI: 10.1002/adem.201600807
  • Microstructure and Mechanical Properties of Fine Structured B4C/2024 Al
           Composites with High B4C Content 
    • Authors: Ruixiao Zheng; Fengmei Ma, Yitan Zhang, Chaoli Ma
      Abstract: In this study, bulk fine structured B4C/2024 Al composites with various B4C content are prepared by mechanical milling and subsequent hot consolidation. Scanning electron microscopy (SEM) observation revealed that the higher the B4C content, the finer the B4C particle size in the bulk composites. Transmission electron microscopy (TEM) observation indicates that the grain size of the Al matrix around the B4C particles is much finer compared to other, area due to the large difference in coefficients of thermal expansion (CTE) between the Al matrix and the B4C particles. Room temperature compression test reveals that with increasing B4C content, the compression strength of the bulk samples first increases and then decreases. The significant change of the mechanical properties is discussed based on the microstructure observed.Bulk fine grained B4C/2024 Al composites with various B4C content are prepared by mechanical milling and subsequent consolidation. The microstructure of the composites can be divided into three zones depending on the microstructural features, which significantly affect the global mechanical properties of the composites.
      PubDate: 2017-04-18T02:45:29.39602-05:0
      DOI: 10.1002/adem.201700047
  • Graphene Platelet (GPL)/Nickel (Ni) Laminate Coatings for Improved Surface
    • Authors: Meng Li; Jian Liu, Xiaoping Zhang, Cunlong Zhou, Sai Priya Munagala, Yaqin Tian, Jie Ren, Kyle Jiang
      Abstract: In this paper, an investigation is reported on graphene platelet (GPL)/nickel (Ni) laminate coatings by electrochemical deposition. Nickel sulphamate baths with and without GPLs are used to produce GPL/Ni coatings with varied layers and pure Ni coatings for comparison. Microstructures, surface roughness, and mechanical performance of the coatings were examined. It is found that GPLs are homogeneously deposited in the Ni matrix. With the addition of GPLs, the surface roughness of the GPL/Ni composites increases while the average grain size of the Ni matrix decreases significantly. A higher hardness of coatings can be obtained by depositing more layers and introducing a higher content of GPLs. The microstructure of GPL/Ni composite coatings exhibits a preferred orientation at (111).In this paper, an investigation is reported on graphene platelet (GPL)/nickel (Ni) multilayer coatings by electrochemical deposition. The schematic of structure of coatings is shown in ToC figure. The research shows the potential of GPLs, as nano fillers for fabrication of composite coatings with excellent mechanical performance, and the preparation of multilayer composites can provide a new way to prepare new composite materials.
      PubDate: 2017-04-18T02:40:30.19909-05:0
      DOI: 10.1002/adem.201600795
  • Synthesis, Microstructure, and Catalytic Performance of Monolithic
           Low-Density Porous Au 
    • Authors: Qin Li; Lixian Lian, Ying Liu, Chaoqing Liu
      Abstract: A series of monolithic porous Au with different pore sizes are successfully synthesized by a facile template-dealloying corrosion method. Spherical Cu particles are employed as sacrificial templates, and a FeCl3–HNO3 two-step corrosion method is developed to dissolve the Cu components. The microstructure and phase evolution, as well as the effect of the corrosive media, are investigated in this study. As a result, the prepared monolithic porous Au possesses ultra-low density and a special hollow porous core-shell structure. When a small-sized template (≈1 μm) is adopted, the corresponding density is as low as 0.37 g cm−3 (1.8% of the full density of Au). In addition, due to the special structure, the monolithic porous Au exhibits good catalytic performance (Kapp = 0.43 min−1), that is, relatively higher than that of most traditional Au-based powder/slurry materials.A series of monolithic porous Au with different pore sizes are successfully synthesized using spherical cu particles, as a new kind of sacrificial templates. A Fecl3–HNO3 two-step corrosion method is developed to dissolve the Cu components. The prepared porous Au bulks possess ultra-low density as low as 0.3 g cm−3 and hollow porous core-shell structure, exhibiting excellent catalytic performance as monolithic catalysts.
      PubDate: 2017-04-18T02:35:40.548879-05:
      DOI: 10.1002/adem.201700045
  • Brazing Graphite to Aluminum Nitride for Thermal Dissipation
    • Authors: Tsung-Te Chou; Wei-Hsing Tuan, Hiroshi Nishikawa, Biing-Jyh Weng
      Abstract: In the present study, graphite paper is joined to aluminum nitride (AlN) using an active Ag–Cu–Ti foil. The Ti in the brazing foil diffuses to AlN side to form titanium nitride, to graphite side to form titanium carbide during bonding. The thermal diffusivity of the AlN–AgCuTi graphite joint is double that of AlN substrate; the resulting thermal conductivity of the joint is, thus, higher. Though the flexural strength of the joint is half that of AlN substrate, it can deflect for 1 mm at a 28 mm span without failure. The large deflection capability can be related to the sliding between graphite sheets within the graphite paperIn the present study, graphite paper is joined to aluminum nitride (AlN) using an active Ag–Cu–Ti foil. The AlN–Ag–Cu–Ti graphite joint exhibits unique thermal and mechanical characteristics.
      PubDate: 2017-04-13T10:11:01.381013-05:
      DOI: 10.1002/adem.201600876
  • Continuous Casting of TiAlNb Alloys with Different Velocities by Mixing
           Binary TiAl Ingot and Nb Wire 
    • Authors: Hong-Ze Fang; Rui-Run Chen, Dong Chai, Yao-Hua Yang, Yan-Qing Su, Hong-Sheng Ding, Jing-Jie Guo, Heng-Zhi Fu
      Abstract: A method of continuous casting is used and the research investigates microstructure and mechanical properties under different drawing velocity (R, mm/min). The results show that microstructure and composition measurement of different zones are uniform. The smallest grain size is 25.93 μm and formability is good with 0.5R. Compressive strength is higher with 0.5R and maximum value is 1697MPa. Fracture toughness with 0.5R improves about 35.7% which is 21.7MPa·m1/2. The fracture morphology is trans-lamellar fracture and interface de-lamination. The method is a feasible way to continuously cast the TiAl-Nb alloys. The R is an important parameter to add high-melting-point element, which affects solidified temperature interval of solidification front and electromagnetic stirring.A method is used to add high-melting-point element into TiAl-based alloy. Microstructure and composition measurement are uniform of liquid phase zone, mushy zone and stability zone with 0.5R. Another image is compressive strength and fracture toughness with different drawing velocity.
      PubDate: 2017-04-10T06:21:24.318075-05:
      DOI: 10.1002/adem.201700058
  • Reproducible Superhydrophobic PVC Coatings; Investigating the Use of
           Plasticizers for Early Stage Biofouling Control
    • Authors: Robert Brown; Sonia Russell, Salina May, Fiona Regan, James Chapman
      Abstract: Here we show an easy to synthesize superhydrophobic material using a solvent phase–separation process of poly vinyl chloride. It is found that solvents mixed in different ratios increase the dielectric value of the solvent and can be tuned to produce superhydrophobic PVC. The PVC solution is then spin-coated onto glass slides for characterization using scanning electron microscopy. Plasticizers are doped into the 70% (v/v) PVC to determine their overall effects; it is found that plasticizers reduce the water contact angle value. The final coatings were tested in a series of antifouling assays in a marine environment lab study; it is found that the superhydrophobic PVC material reduced marine biofouling.The paper investigates the influence of surface hydrophobicity as a mechanism to reduce early stage marine biofouling. A solvent phase separation process to produce superhydrophobic water contact angle values (>150°) is performed and the materials show less early stage marine biofouling.
      PubDate: 2017-04-07T03:42:05.577989-05:
      DOI: 10.1002/adem.201700053
  • Nanoporous Surface Modifications through Dealloying of Al–Ti
    • Authors: Wei Zhao; Nianqi Liu, Jiacheng Rong, Lei E, Dan Zhao
      Abstract: TiO2 nanoporous structure was formed on the surface of Al–Ti alloy through a facile chemical corrosion method. The alloy composition, NaOH concentration, reaction time, and temperature played important roles in determining the morphology, elemental composition, phase composition, and the hydrophilic properties of the as-dealloyed samples. A uniform pore size distribution of a three-dimensional network structure was obtained with the diameter ranged from 100 nm to 2 μm. The obtained TiO2-based crystalline material exhibited good surface hydrophilic activity and light absorbency, which opened avenues in formation of porous nanostructures with high performance and low cost.A facile method for modifying TiO2 nano-porous surface is presented by chemical corrosion of Al–Ti alloy. The pores with three-dimensional continuous network in surface can be developed through controlling the Al content and alkali concentration, which may lead to a good surface hydrophilicity and light absorbance.
      PubDate: 2017-04-06T08:16:29.395702-05:
      DOI: 10.1002/adem.201600866
  • A Micromechanical Approach Investigating the Effects of Percolating
           Eutectic Network on Mechanical Behavior of Magnesium Alloys
    • Authors: Bao Zhang
      Abstract: A novel two-dimensional (2D) micromechanical model presented is capable of predicting eutectic network strength and structural efficiency consistent with computed results on the basis of three-dimensional (3D) actual morphology of eutectic network, and shows considerable advantages in terms of efficiency, practicability and computation cost. Another critical advantage lies in the capability of evaluating network-matrix interaction and the incorporation of interaction strength leads to an improved agreement between numerical and experimental flow behavior of the Mg alloy. The analysis also suggests that network-matrix interaction is comparable with dispersion and network strengthening with respect to the contribution to alloy yield strength.A micromechanical model proposed is capable of assessing the deformation behavior and structural efficiency of eutectic network formed in high pressure die cast Mg alloys, and more importantly, reveals the strength due to network-matrix interaction, that is, comparable with other strengthening effects.
      PubDate: 2017-04-06T08:16:27.310402-05:
      DOI: 10.1002/adem.201600871
  • Influence of Erbium, Cerium on the Stress Corrosion Cracking Behavior of
           AZ91 Alloy in Humid Atmosphere 
    • Authors: Yulai Song; Zhen Wang, Yaohui Liu, Miao Yang, Qingxiang Qu
      Abstract: AZ91 magnesium alloys modified by Er and Ce are fabricated (referred to as AZErCe) and their stress corrosion cracking (SCC) behaviors are studied by slow strain rate tensile (SSRT) method in air, humid atmosphere with and without chloride. The addition of Er and Ce promotes the formation of Al3Er and Al11Ce3 phase and reduces both the size and the volume fraction of β-phase. AZErCe possess improved corrosion resistance and passivation characteristic compared to AZ91 due to the reduced micro-galvanic corrosion and the more protective films. SSRT tests demonstrate that the joint addition of Er and Ce effectively improve the SCC resistance of AZ91 alloy. In particular, the representative fractography of AZErCe exhibits lesser effect of hydrogen embrittlement than AZ91. The improved SCC resistance of AZErCe can be ascribed to the presence of Er and Ce, which alleviate corrosion of Mg matrix and thus weaken the effect of hydrogen embrittlement on SCC resistance.Compared with the microstructure of as-cast AZ91 alloy, the addition of Er and Ce can significantly reduce the volume fraction and the size of β-phase and facilitate the formation of Al3Er and Al11Ce3 intermetallic compounds, which are easily distinguished by white color from gray β-phase. All of these changes exert positive effect on SCC resistance of AZ91 alloy.
      PubDate: 2017-04-05T07:55:57.202949-05:
      DOI: 10.1002/adem.201700021
  • Tough Nano-Architectured Conductive Textile Made by Capillary Splicing of
           Carbon Nanotubes 
    • Authors: Yue Liang; David Sias, Ping Ju Chen, Sameh Tawfick
      Abstract: Flexible electronics require electrically conductive and mechanically reliable nanoscale thin films. However, thin metal films have low fracture energy, which limits the performance of flexible devices. We demonstrate the design and synthesis of highly conductive, strong and tough nano-architectured textile by capillary splicing of aligned carbon nanotubes (CNT). Owing to the strong van der Waals forces among CNTs, the pristine CNT network has average strength of 170 MPa. The average fracture energy of the textile is 16 kJ/m2, 50 folds higher than metal nanofilms. The high toughness results from crack bifurcations and friction hysteresis in a dissipation zone propagating several millimeters ahead of the crack tip. This material is suitable for applications ranging from smart skin and flexible sensors.Flexible electronics require thin conductive and structurally reliable materials. However, thin metal films have low fracture energy and limited ductility. A bio-inspired design is demonstrated for the fabrication of strong, tough, and highly conductive carbon nanotube textile based on a nano-architectured network. The architectured textile has a fracture energy 50 folds higher than thin metal films at a fraction of the density.
      PubDate: 2017-04-05T03:55:42.229035-05:
      DOI: 10.1002/adem.201600845
  • Developing Breathable Double-Layered Fibrous Membranes Equipped with Water
           Pulling Mechanism Toward Clothing with Enhanced Comfort
    • Authors: Hossein Fashandi; Amir Reza Ghomi
      Abstract: Quick transfer of sweat from skin to atmosphere and dryness of textile inner surface are of scientific and commercial interests. However, creating a balance between these two parameters remains a serious challenge. In this work, electrospun double-layered membranes constructed of poly(vinylidene fluoride) fibrous layer (as inner hydrophobic layer) and nylon6 nanofibrous layer (as outer hydrophilic layer) are produced. Once a thin hydrophobic layer is considered, the enhanced water pulling mechanism is balanced out by increased wetted area in the inner surface. This is handled through selecting an optimum thickness for the inner layer. The designed double-layered membrane is a promising candidate for developing modern breathable textiles with enhanced moisture management properties such as sportswear.Developing electrospun fibrous structures with the ability of quick sweat transfer from skin to atmosphere and dryness of inner surface is the main goal of the present research work. This is implemented through manufacturing double-layered fibrous membranes composed of a poly(vinylidene fluoride) hydrophobic layer and a nylon6 hydrophilic layer. The produced sample is a promising candidate for developing modern breathable textiles such as sportswear.
      PubDate: 2017-04-05T03:51:12.317096-05:
      DOI: 10.1002/adem.201600863
  • Initiated Chemical Vapor Deposition of Polymer Films at High Process
           Temperature for the Fabrication of Organic/Inorganic Multilayer Thin Film
    • Authors: Bong Jun Kim; Hyejeong Seong, Hyunjeong Shim, Young Il Lee, Sung Gap Im
      Abstract: For the fabrication of thin film encapsulation (TFE), sequential deposition of organic and inorganic layers is inevitable. A single-chamber system of initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) is reported previously. Here, the substrate temperature (Ts) of the iCVD is aligned with that of ALD to facilitate the transition of the deposition mode by removing delays caused by repeated heating/cooling of the substrate. While increasing the Ts of iCVD from 40 to 90 °C, the process pressure is optimized so that the properties of the organic film are unchanged from that deposited with 40 °C. The Ts alignment significantly reduced the time delay during transition of the deposition mode, and the fabrication of the TFE is expedited.Within a single-chamber system capable of both initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) processes, the substrate temperature of iCVD is increased to 90 °C to equalize the process temperature with ALD. The transition between organic and inorganic layer deposition modes is facilitated without any loss of barrier property of the fabricated multilayer thin film encapsulation.
      PubDate: 2017-03-31T07:10:30.288291-05:
      DOI: 10.1002/adem.201600870
  • Inkjet and Aerosol Jet Printing of Electrochemical Devices for Energy
           Conversion and Storage 
    • Authors: L. Jay Deiner; Thomas L. Reitz
      Abstract: Inkjet and aerosol jet printing have recently emerged as promising fabrication techniques for a broad range of devices for electrochemical energy conversion and storage – batteries, fuel cells, and supercapacitors. If fully realized, these printing techniques may enable device performance advantages accruing from precise micron scale patterning, thin layer deposition, and materials grading. Printing may also allow scalable, low materials waste manufacturing, and conformal integration of power elements into structural elements. This article reviews the fundamental capabilities of inkjet and aerosol jet printing relevant to electrochemical devices, surveys current literature, and presents future challenges which must be tackled to achieve high performance, printed electrochemical energy storage, and conversion devices.Inkjet and aerosol jet printing are emerging methods for the fabrication of batteries, fuel cells, and supercapacitors. These direct-write methods show particular promise because they enable low cost, conformal deposition of materials within the lengthscales that are important for electrochemical device performance improvement and structural integration. At the macroscale, inkjet and aerosol jet printing allow for maskless deposition on a range of substrates. At the mesoscale, they facilitate functional grading at and beyond electrode/electrolyte interfaces. At the microscale, they permit thin layer deposition and extension of the electrode/electrolyte interfacial area.
      PubDate: 2017-03-31T07:05:48.222431-05:
      DOI: 10.1002/adem.201600878
  • Effects of Solution Treatment on the Microstructure and Mechanical
           Properties of Ti–22Al–25Nb Alloys 
    • Authors: Yang Wu; Hongchao Kou, Bin Tang, Degui Liu, Jizhen Li, Jinshan Li
      Abstract: The effects of solution treatment on the microstructure and mechanical properties of Ti-22Al-25Nb alloy are investigated. Numerous equiaxed α2 particles distribute in a B2 matrix after solution treatment in the α2 + B2 region. The growth rate of the B2 grain increases with solution temperature and decreases with increasing holding time. When the solution temperature is lower than B2-transus, it is seen that both the strength and ductility decrease with increasing solution temperature and holding time. After being solution-treated at a super-transus temperature, the alloy with a fully B2 microstructure shows an ultralow elongation (∼5%) and a typical brittle fracture characteristic.For Ti–22Al–25Nb alloy, α2 phase dissolves gradually and the average grain size of B2 phase increases with increasing solution temperature and time. The pinning of some α2 particles at the B2 grain boundaries results in abnormal grain growth (AGG). Furthermore, various microstructure characteristics have significant influence on room temperature tensile properties.
      PubDate: 2017-03-30T04:35:49.507818-05:
      DOI: 10.1002/adem.201700081
  • Alloying Effects on the Phase Transformation Behaviors of the Orthorhombic
           and Ordered ω Phases in High Nb–TiAl Alloys 
    • Authors: Xingguo Hu; Jinshan Li, Lin Song, Tiebang Zhang, Hongchao Kou
      Abstract: In this work, alloying effects of Mn, Mo, and Cr on the phase transformation behaviors of the orthorhombic and ordered ω phases in high Nb–TiAl are investigated. Modulated structures are observed in the Mn and Mo-containing alloys indicating that Mn and Mo cannot hinder the formation of the orthorhombic phase while Cr hinders the formation of the orthorhombic phase completely. For the ordered ω phases, small ordered ω particles are observed in the Mn-containing alloy. Though Mn cannot hinder the formation of the ordered ω phases, the formation temperature of which is decreased to 600 °C. No ordered ω phases are observed in the Mo and Cr-containing alloys. Two percent of Mo and Cr hinder the formation of the ordered ω phases completely. The stabilization effect of Mn, Mo, and Cr on βo phase is mainly a thermodynamic effect.Alloying effects of Mn, Mo, and Cr on the phase transformation behaviors of the orthorhombic and ordered ω phases are investigated. Mn and Mo cannot suppress the formation of the orthorhombic phase. Only in the 2Mn alloy are the ordered ω phases observed. The stabilization effect on the βo phase is concluded to be a thermodynamic effect.
      PubDate: 2017-03-30T04:30:33.033534-05:
      DOI: 10.1002/adem.201700040
  • Effect of Severe Plastic Deformation and Subsequent Silicon Spheroidizing
           Treatment on the Microstructure and Mechanical Properties of an
           Al–Si–Mg Alloy 
    • Authors: Nima Haghdadi; Abbas Zarei-Hanzaki, Megumi Kawasaki, Andre B. Phillion, Peter D. Hodgson
      Abstract: This study investigated the synergetic effects of severe plastic deformation and subsequent heat treatment on the characteristics of an A356 alloy. The severe deformation by accumulative back extrusion (ABE) at 300 °C substantially refined the α–Al primary phase and Si particles, but did not homogeneously redistribute the Si particles. ABE also improved the strength but did not enhance the ductility. To make a compromise between strength and ductility, a subsequent heat treatment at 540 °C was carried out. It was shown that severe plastic deformation substantially accelerated the silicon spheroidization. Heat treatment increased the ductility of the material from ∼8% (in the deformed condition) to ∼15%. This was discussed with emphasis on restoration of the matrix, spheroidization of the Si particles, and redistribution of the Si particles within the α–Al matrix.In order to make a compromise between strength and ductility, a subsequent heat treatment is carried out on a severely deformed A356 alloy. Heat treatment for 2 min at 540 °C changes the fracture mode from brittle to ductile, makes cracks to propagate intragranularly, and, in turn, enhances the ductility of the material from ≈8% to ≈15%.
      PubDate: 2017-03-28T07:15:28.635731-05:
      DOI: 10.1002/adem.201700064
  • Evaluation of Textural Effect on the Rollability of AZ31 Alloys by
           Wedge-Shaped Sample Design 
    • Authors: Renlong Xin; Maoyin Wang, Zhe Liu, Xingpin Chen, Guangjie Huang, Qing Liu
      Abstract: This paper aims to compare the textural effect on the rollability of Mg alloy sheets at different temperatures. Wedge-shaped AZ31 alloy plates with two kinds of initial textures are designed and rolled at five different temperatures. Then, the rollability under different conditions can be evaluated by observing the development of edge-cracks. The results show that the initial texture has little influence on the single-pass rollability at low temperatures (100 and 150 °C), while the influence is significant for rolling above 150 °C. Schmid factor and in-grain misorientation axis analyses revealed that the textural effect on the activation of prismatic glide accounted for the observed distinct rollability at elevated temperatures.Wedge-shaped AZ31 alloy plates with two kinds of initial textures are designed and rolled at five different temperatures. Then, the rollability under different conditions can be evaluated by observing the development of edge-cracks. It shows that the initial texture has little influence on the single-pass rollability at low temperatures, while the influence was significant for rolling above 150 °C.
      PubDate: 2017-03-24T05:15:14.36925-05:0
      DOI: 10.1002/adem.201700035
  • A High Strength Ti–SiC Metal Matrix Composite 
    • Authors: Khandaker Mezanur Rahman; Vassili A. Vorontsov, Stephen. M. Flitcroft, David Dye
      Abstract: A SiC reinforced Ti-5Al-5Mo-5V-3Cr matrix metal matrix composite is developed. Monolithic blocks of alloy are hot rolled via pack rolling to produce foils for MMC panel fabrication. These are consolidated using hot isostatic pressing and solution treated and aged for optimum strength. The panels exhibited a strength of 2 GPa in tension and 3.5 GPa in compression, compared to the aerospace steel 300M, which has a tensile strength of 1.69 GPa. The fatigue performance of the material exceeded that of MMCs developed using Ti-21S or Ti-6Al-4V matrices. Finally, the reaction zone between the SiC and matrix is examined, revealing the presence of TiC.A metal matrix composite is produced using a titanium matrix and silicon carbide reinforcement. A cheaper foil fibre foil layup method is used. The resultant material had a tensile strength in excess of 2GPa with excellent fatigue properties.
      PubDate: 2017-03-22T03:40:43.588538-05:
      DOI: 10.1002/adem.201700027
  • Nano-Hydroxyapatite and TiO2 Bioactivated Polymer for Implant Applications
    • Authors: Suzan Bsat; Jennifer McTaggart, Xiao Huang
      Abstract: Polymers have been successfully used for implant applications, however, challenges remain as their design requires a delicate balance between mechanical, chemical, and physical properties to ensure cell survival and tissue formation. Additive manufacturing techniques, such as SLA, offer the opportunity to achieve desired physical and mechanical properties because of the precision and control over architecture. Such control allows manipulation over the distribution of mechanical properties throughout the implant. PMA/HA and PMA/TiO2 solid and porous structures are, therefore, manufactured using room temperature SLA techniques. HA and TiO2 are added to the polymer for bio-functionalizing purposes. The apatite forming ability of the samples are evaluated using HBSS immersion. All PMA and PMA/TiO2 samples does not show any bioactivity in terms of apatite formation, although limited amounts of CaO is found on PMA surfaces. PMA/HA samples demonstrate bioactivity with newly formed apatite formation observed after 3 and 5 week HBSS immersion.PMA, PMA/TiO2, and PMA/HA polymer structures for implant applications are fabricated using SLA technique. Following HBSS immersion, PMA/HA composite has an abundance of calcium phosphate mineral formation as compared to PMA and PMA/TiO2, based on SEM and EDS results. Future studies will focus on optimizing PMA/HA polymer structure to obtain desired physical and mechanical properties.
      PubDate: 2017-03-20T08:21:01.908749-05:
      DOI: 10.1002/adem.201600727
  • Effect of Ti and Zr Combined Modification on Microstructures and
           Mechanical Properties of Mg95Y2.5Zn2.5 Alloy Containing LPSO and W
    • Authors: Shouzhong Wu; Yanbin Ma, Jinshan Zhang, Chunxiang Xu, Xiaofeng Niu, Wei Liu
      Abstract: In order to develop a high performance Mg–Y–Zn alloy containing LPSO phase in the condition of lower Y/Zn atomic ratio, the effect of Ti and Zr on microstructures and mechanical properties of Mg95Y2.5Zn2.5 alloy was investigated. Although the α-Mg grains can be refined by adding Ti and Zr separately, the best refinement effect can be obtained by the combined addition of them. More importantly, the formation of LPSO phase was promoted by adding them in as-cast Mg95Y2.5Zn2.5 alloy. Meanwhile, the growth model of W phase was transformed from divorced eutectic to cooperative eutectic. In this case, the LPSO/W interface became continuous, which degraded the mechanical properties of as-cast alloys. After extrusion, the increased LPSO phase caused by adding Ti and Zr greatly improved the strength of as-extruded alloy.Mg93.1Y2.5Zn2.5Ti1.6Zr0.3 alloy has the best refinement effect due to the combined addition of Ti and Zr. Meanwhile, Ti and Zr promote the formation of LPSO and change the growth model of W phase. The increased LPSO phase does not enhance mechanical properties of as-cast alloy, but rather greatly improves mechanical properties of as-extruded alloy.
      PubDate: 2017-03-16T06:51:24.521429-05:
      DOI: 10.1002/adem.201600839
  • Microstructure and Crystallography of α Phase Nucleated Dynamically
           during Thermo-Mechanical Treatments in Metastable β Titanium Alloy 
    • Authors: Jiangkun Fan; Jinshan Li, Yudong Zhang, Hongchao Kou, Lionel Germain, Nathalie Siredey-Schwaller, Claude Esling
      Abstract: The α phase nucleated dynamically during the thermo–mechanical coupling process in titanium alloy is really interesting but difficult to sufficiently ascertain. In the present work, the α phase nucleation behavior, the orientation relationship between α/β as well as the phase transformation kinetics during hot deformation of Ti-5553 alloy were investigated in-depth. Results reveal that the “necklace” microstructure formed. The Burgers orientation relationship between α/β phases has been destroyed gradually. The β  α phase transformation is obviously retarded during the hot compression due to the competitive effect of softening process (dynamic recovery/recrystallization). These results could provide valuable reference for process optimization and the microstructural evolution controlling.The dynamic nucleation and evolution of α phase during hot deformation is totally different from heat treatment. The “necklace” microstructure forms and the Burgers orientation relationship between α/β is destroyed. There is a competitive mechanism between β  α phase transformation and DRV/DRX.
      PubDate: 2017-03-15T09:35:37.966941-05:
      DOI: 10.1002/adem.201600859
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