Subjects -> METALLURGY (Total: 58 journals)
Showing 1 - 10 of 10 Journals sorted alphabetically
Acta Metallurgica Slovaca     Open Access   (Followers: 2)
Advanced Device Materials     Open Access   (Followers: 6)
American Journal of Fluid Dynamics     Open Access   (Followers: 44)
Archives of Metallurgy and Materials     Open Access   (Followers: 9)
Asian Journal of Materials Science     Open Access   (Followers: 4)
Canadian Metallurgical Quarterly     Hybrid Journal   (Followers: 21)
Complex Metals     Open Access   (Followers: 2)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 24)
Graphene and 2D Materials     Open Access   (Followers: 6)
Handbook of Ferromagnetic Materials     Full-text available via subscription   (Followers: 1)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2)
High Temperature Materials and Processes     Open Access   (Followers: 6)
Indian Journal of Engineering and Materials Sciences (IJEMS)     Open Access   (Followers: 11)
International Journal of Metallurgy and Alloys     Full-text available via subscription   (Followers: 1)
International Journal of Metals     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 11)
International Journal of Mining and Geo-Engineering     Open Access   (Followers: 4)
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 5)
ISIJ International - Iron and Steel Institute of Japan     Full-text available via subscription   (Followers: 26)
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)     Full-text available via subscription   (Followers: 2)
JOM Journal of the Minerals, Metals and Materials Society     Hybrid Journal   (Followers: 35)
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Cluster Science     Hybrid Journal  
Journal of Heavy Metal Toxicity and Diseases     Open Access  
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 11)
Journal of Materials & Metallurgical Engineering     Full-text available via subscription   (Followers: 2)
Journal of Materials Processing Technology     Hybrid Journal   (Followers: 21)
Journal of Metallurgical Engineering     Open Access   (Followers: 4)
Journal of Sustainable Metallurgy     Hybrid Journal   (Followers: 3)
Materials Science and Metallurgy Engineering     Open Access   (Followers: 6)
Metal Finishing     Full-text available via subscription   (Followers: 20)
Metallurgical and Materials Engineering     Open Access   (Followers: 7)
Metallurgical and Materials Transactions A     Hybrid Journal   (Followers: 41)
Metallurgical and Materials Transactions B     Hybrid Journal   (Followers: 32)
Metallurgical and Materials Transactions E     Full-text available via subscription   (Followers: 2)
Metallurgical Research and Technology     Full-text available via subscription   (Followers: 8)
Metallurgy and Foundry Engineering     Open Access   (Followers: 2)
Mining, Metallurgy & Exploration     Hybrid Journal  
Powder Diffraction     Full-text available via subscription   (Followers: 1)
Powder Metallurgy     Hybrid Journal   (Followers: 36)
Powder Metallurgy and Metal Ceramics     Hybrid Journal   (Followers: 8)
Powder Metallurgy Progress     Open Access   (Followers: 5)
Practical Metallography     Full-text available via subscription   (Followers: 6)
Rare Metals     Hybrid Journal   (Followers: 3)
Revista de Metalurgia     Open Access  
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Revista Remetallica     Open Access   (Followers: 1)
Revue de Métallurgie     Full-text available via subscription  
Russian Metallurgy (Metally)     Full-text available via subscription   (Followers: 4)
Science and Technology of Welding and Joining     Hybrid Journal   (Followers: 7)
Steel Times lnternational     Partially Free   (Followers: 19)
Transactions of the IMF     Hybrid Journal   (Followers: 14)
Transactions of the Indian Institute of Metals     Hybrid Journal   (Followers: 5)
Tungsten     Hybrid Journal  
Universal Journal of Materials Science     Open Access   (Followers: 3)
Welding in the World     Hybrid Journal   (Followers: 7)
Welding International     Hybrid Journal   (Followers: 11)
Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки     Open Access  
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Metallurgical and Materials Transactions A
Journal Prestige (SJR): 1.093
Citation Impact (citeScore): 2
Number of Followers: 41  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1543-1940 - ISSN (Online) 1073-5623
Published by Springer-Verlag Homepage  [2626 journals]
  • Effect of Solute Carbon on the Characteristic Hardening of Steel at High
           Temperature
    • Abstract: Small ball rebound hardness tests demonstrated characteristic hardening at 700 K in the ultra-low carbon and pearlitic steels. The equilibrium phase diagram of Fe-C binary alloy calculated using Thermo-Calc exhibited dissolving of cementite above 700 K. Moreover, in-situ heating neutron diffraction measurement demonstrated the increase of lattice parameter by dissolving of cementite above 700 K. Therefore, it can be concluded that the characteristic hardening above 700 K can be attributed to the solid solute carbon.
      PubDate: 2021-01-13
       
  • Semi-solid Constitutive Parameters and Failure Behavior of a Cast AA7050
           Alloy
    • Abstract: Abstract AA7050 is an aluminum alloy with superior mechanical properties; however, it is prone to hot tearing (HT) during its production via direct-chill casting. This study focuses on extracting constitutive parameters of the alloy thermomechanical behavior in semi-solid state as well as gaining insight in its failure behavior. Tensile tests were performed using an Instron 5944 at solid fractions between 0.85 (550 °C) and 1.0 (465 °C), at deformation rates of 0.2 and 2 mm/min. The results showed that there are three mechanical behavior regimes in this solid fraction range: ductile at 1.0 (T = 465 °C) ≤ fs < 0.97 (T = 473 °C), brittle at 0.97 (T = 473 °C) ≤ fs ≤ 0.9 (T = 485 °C) and then ductile again (at 0.9 (T = 485 °C) < fs ≤ 0.85 (T = 550 °C)). Fracture surface analysis revealed that the fracture mode was mostly intergranular with fracture propagating through solid bridges as well. Semi-solid constitutive parameters were obtained by making a simple thermal model and numerical tensile tests in ALSIM software package and comparing the simulation results with experimental mechanical tests. The extracted constitutive parameters and available information from the literature support the fact that AA7050 is more susceptible to HT than AA5182 and Al-2 wt pct Cu alloys. The obtained parameters can further enhance the predictive capability of computer simulations of direct-chill casting.
      PubDate: 2021-01-08
       
  • Machine Learning Approach to Design High Entropy Alloys with Heterogeneous
           Grain Structures
    • Abstract: Abstract Heterogeneous nanocrystalline high-entropy alloys (HEAs) have excellent mechanical properties. However, it is still difficult to obtain the optimized grain size in the heterogeneous-grained HEAs, which achieves their outstanding mechanical properties. Here, using a novel integration method of machine learning, a physical model and atomic simulation, the optimal grain size is designed for achieving high yield strength of heterogeneous-grained CrCoFeNi HEAs. Atomic simulations give the stress–strain curve, yielding strength and microstructure with the increase of small grain size. The physical-based strength model expands the data from the atomic simulations and obtains the transition region from the Hall–Petch to inverse Hall–Petch relationship. The results show that the strength of CrCoFeNi HEAs derives mainly from the contribution of the grain boundary compared to lattice friction stress. The machine learning model shows that the obvious transition point from the Hall–Petch to inverse Hall–Petch relationship occurs at the grain size of 38.4 nm for the heterogeneous-grained CrCoFeNi HEAs with the large grain size of 165 nm. This result agrees with the prediction from the subsequent atomic simulation. This integrated model makes significant contributions to understanding deformation and designing the microstructure of heterogeneous-grained HEAs. Importantly, the developed model including simulation, a theoretical model, experiment and machine learning can be widely applied to explore the advanced material with the desired performance.
      PubDate: 2021-01-07
       
  • Origins of Non-random Particle Distributions and Implications to Abnormal
           Grain Growth in an Al-3.5 Wt Pct Cu Alloy
    • Abstract: Abstract The mechanisms of abnormal grain growth (AGG) in particle-containing systems have long been a mystery. Recently, we reported that a non-random particle distribution can induce a grain size advantage and trigger AGG. However, the processing conditions leading to a non-random particle distribution are far from being understood. Here, we investigate the particle distribution and concomitant grain growth behavior at different annealing temperatures and times in an Al-3.5 wt pct Cu alloy by scanning electron microscopy (SEM). At high temperatures and long times, the particle distribution evolves from random to non-random, with an accompanying transition from normal grain growth (NGG) to AGG. Analytical calculations suggest that a non-random particle distribution is introduced by residual Cu segregation even after homogenization. In short, the corresponding fluctuation of θ-Al2Cu phase distribution is amplified at elevated temperatures via particle dissolution. We quantify the spatial inhomogeneity of particles through the Gini coefficient and link this important parameter to the critical grain size necessary for AGG. The trends are conveyed succinctly in a temperature–time–(structural) transformation (TTT) diagram, which identifies the onset of AGG in an Al-3.5 wt pct Cu alloy.
      PubDate: 2021-01-07
       
  • Effects of High-Concentration Cu and Sn on the Nucleation and Growth
           Behavior of Graphite on Rare-Earth Compounds During the Solidification of
           Cast Iron
    • Abstract: Abstract Ferrous scraps have been widely utilized as raw materials in the production of ductile irons. With increasing scrap use and repeated recycling, the concentrations of tramp elements such as copper (Cu) and tin (Sn) in the raw materials are expected to increase as they cannot be easily removed through conventional refining processes. To obtain fundamental insights into the effects of high-concentration Cu (up to 2.0 wt pct) and Sn (up to 1.0 wt pct) on the nucleation and growth of graphite on a foreign substrate, a novel approach through contact-melting of cast iron on lanthanum oxide (La2O3) substrate is utilized to study graphite nucleation and growth behavior at the alloy/substrate interface and in the bulk alloy. Enhanced graphitization at the alloy/substrate interface and in the bulk alloy are observed at varying Cu content. Copper promotes graphitization in cast iron by elevating the equilibrium liquidus temperature of graphite (TG) and increasing the carbon supersaturation (ΔC). On the other hand, Sn demonstrates stronger graphitizing effects than Cu as only a lower concentration of Sn is required to achieve a similar increase of TG and ΔC. More significantly, Sn enhances graphite nodule counts in the bulk alloy through the formation of fine La-Sn intermetallic compounds which act as effective sites for graphite nucleation.
      PubDate: 2021-01-06
       
  • Directional Solidification of a Nickel-Based Superalloy Product Structure
           Fabricated on Stainless Steel Substrate by Electron Beam Additive
           Manufacturing
    • Abstract: Abstract This article is the first to apply wire-feed electron beam additive manufacturing in vacuum to fabricate a part from a complex nickel-based superalloy with directional structure on a stainless steel substrate. It is shown that the determining factor for the formation of parts with directional structure is the local metallurgy conditions implemented in electron beam additive manufacturing. These conditions are the magnitude and direction of the temperature gradient as well as the geometry (shape) of the solidification front in the molten pool. The substrate effect (both chemical and structural) on the composition and structure of the part material is cancelled out at a distance not exceeding 8.0 mm from the substrate. Thus, the proposed 3D printing method is quite acceptable for the manufacturing of parts from heat-resistant nickel alloys with directional structure on substrates made of less expensive materials.
      PubDate: 2021-01-04
       
  • Effect of Pulse Frequency on the Columnar-to-Equiaxed Transition and
           Microstructure Formation in Quasi-Continuous-Wave Laser Powder Deposition
           of Single-Crystal Superalloy
    • Abstract: Abstract The columnar-to-equiaxed transition (CET) plays a vital role in keeping the monocrystalline nature in the repaired single-crystal superalloy by the laser powder deposition process. In this study, the effect of pulse frequency on the CET and microstructure formation in a novel quasi-continuous-wave laser powder deposition process of single-crystal superalloy was studied through an improved three-dimensional mathematical model and corresponding experiments. Results showed that the pulse frequency has a predominant effect on the CET conditions and associated microstructure formation in the deposited bead. In each pulse cycle, the CET position at the solidification interface moves upward synchronously with the contraction of the molten pool, tending to induce the epitaxial growth of columnar dendrites with a tapered distribution. The overlaps of adjacent pulsed molten pools contribute to the undulated distribution of columnar dendrites in the deposited bead. The increase of pulse frequency weakens the oblique fluctuation of CET positions and resultantly narrows the undulated distribution of epitaxial columnar dendrites. Under the given conditions, the height ratio of epitaxial columnar dendrites obtains a minimum value of 71 pct with pulse frequency = 50 Hz and has a minimum value of 50 pct with pulse frequency = 0 Hz (continuous-wave mode), indicating that the quasi-continuous-wave laser mode can effectively enhance the epitaxial growth ability of columnar dendrites with the optimized pulse frequency. The quasi-continuous-wave laser powder deposition process exhibits an attractive capability to balance deposition efficiency and epitaxial growth continuity in the deposited beads. Our results provide a potential method to tailor the CET conditions and optimize the laser repair processing window for the single-crystal superalloy via adjusting the pulse frequency of the quasi-continuous-wave laser.
      PubDate: 2021-01-03
       
  • Hot Tearing Behavior in Double Ternary Eutectic Alloy System: Al-Mg-Si
           Alloys
    • Abstract: Abstract The hot tearing behavior of the double ternary eutectic alloy system, Al-6Mg-xSi (0 to 6.0 wt pct Si) alloys, was evaluated by a constrained rod casting mold equipped with a thermocouple and a load cell connected to a data acquisition system. Experimental results were compared with the results calculated by Scheil’s model using Pandat software to predict the occurrence of hot tearing in Al-6Mg-xSi alloys. The curve of hot tearing susceptibility contained two peaks, which were mainly affected by the double ternary eutectic reactions and the solidification phases evolution. And it agreed with the Kou’s hot tearing index precisely. The types and fractions of solidification phases (Al3Mg2, Mg2Si, and eutectic Si) determined by the addition of Si content changed the freezing range and eutectic liquid fraction greatly. In addition, the types, fractions, sizes, and distributions of solidification phases affected the nucleation, propagation, and healing of hot tear cracks. The maximum contraction force value decreased as the reduction of volume shrinkage coefficient due to the addition of Si content. The drop-in force value on the contraction force curve could indicate the occurrence of hot tearing, and predict the hot tearing susceptibility when considering the shrinkage coefficient.
      PubDate: 2021-01-03
       
  • In Situ Study on Interrupted Growth Behavior and Crystallography of
           Bainite
    • Abstract: Abstract The growth behavior and crystallographic orientation of bainite in a low carbon steel were investigated by a combination of in situ observation and electron backscattered diffraction. The intersection of different bainitic ferrite (BF) laths was analyzed in detail. The results show that the growth of a given lath stops when it runs into a preexisting lath of bainitic ferrite. Growth resumes, after a short stasis, through the nucleation of a new lath on the other side of the obstructing lath. The newly nucleated lath has been termed BF-clone because it shares the same crystallographic orientation with the prior bainitic lath. The nucleation of the BF-clone is promoted by the accumulated transformation strain in the region where the growing lath intersected the pre-existing lath. During the growth of the bainitic ferrite laths, the transformation strain was accommodated through the formation of twin-related variant pairs, which formed one after another with the identical lengthening rates.
      PubDate: 2021-01-03
       
  • Determination of Threshold Pressure for Infiltration of NaCl Preforms by a
           Zinc Base Alloy and its Effect on Young´s Modulus by Numerical Simulation
           
    • Abstract: Abstract The capillary infiltration of the Zn-22Al-2Cu (Zinalco) alloy into NaCl packed particles of sizes 496, 687, and 945 μm was studied using centrifugal casting. The threshold pressure for infiltration of NaCl particles with Zinalco was deduced experimentally, which increased as the diameter of the particles decreased. The work of immersion was determined from the threshold pressure with a value of 2.1. The infiltration proceeded at distinctly different rates for the three particle sizes studied. An equation to predict the threshold pressure to infiltrate Zinalco alloy into NaCl particles for given particle size and volume fraction was established. The micromechanical analysis showed that the strength of the foam depended strongly on the level of infiltration of the derived foam. As the level of infiltration increased, the stress distribution in the foams produced became homogeneously distributed in all the struts that make up the cell, which increases the strength of foam. The elastic modulus of the as-produced Zinalco foams is governed by structural parameters such as the pore size and the strut length. Thinner and shorter struts in the foam increase its ability to resist elastic deformation in the foam.
      PubDate: 2021-01-03
       
  • Fracture Resistance of Advanced High-Strength Steel Sheets for Automotive
           Applications
    • Abstract: Abstract The fracture resistance of different advanced high-strength steel (AHSS) sheets for automotive applications is investigated through conventional tensile tests, fracture toughness measurements, and hole expansion tests. Different fracture-related parameters, such as the true fracture strain (TFS), the true thickness strain (TTS), the fracture toughness at crack initiation (w e i ), the specific essential work of fracture (we), and the hole expansion ratio (HER), are assessed. The specific essential work of fracture (we) is shown to be a suitable parameter to evaluate the local formability and fracture resistance of AHSS. The results reveal that fracture toughness cannot be estimated from any of the parameters derived from tensile tests and show the importance of microstructural features on crack propagation resistance. Based on the relation fracture toughness-local formability, a new AHSS classification mapping accounting for global formability and cracking resistance is proposed. Furthermore, a physically motivated fracture criterion for edge-cracking prediction, based on thickness strain measurements in fatigue pre-cracked DENT specimens, is proposed.
      PubDate: 2021-01-03
       
  • Anomalous Tension Twinning Activity in Extruded Mg Sheet During
           Hard-Orientation Loading at Room Temperature
    • Abstract: The surface twins were characterized for a strongly basal-textured Mg sheet that was deformed under tension in the extrusion direction (hard-orientation). All the twins observed were tension twins. A significant number of them exhibited negative Schmid factor (m) and Luster–Morris parameter (m′) values. Both a normalized m and grain-boundary misorientation were correlated to the twinning behavior, which was shown to be more dependent on the local conditions than the globally applied stress, thereby limiting the m and m′ correlations. Graphic
      PubDate: 2021-01-03
       
  • Relationship Among Tensile Strength, High Cycle Fatigue Strength, and
           Origin of Fatigue Crack Initiation in a Minor Boron (B)-Modified β-Type
           Ti-6.8Mo-4.5Fe-1.5Al Alloy
    • Abstract: Abstract One concern regarding boron (B)-modified Ti alloys is that TiB formed in the alloy could cause early fatigue crack initiation, especially when its tensile strength is considerably higher than 1100 MPa. Therefore, the present study was undertaken to determine whether TiB could indeed become an origin of fatigue crack initiation in a high strength 0.1 pct B-modified β-type Ti-6.8Mo-4.5Fe-1.5Al alloy. An alloy with or without B was subjected to different types of heat treatments to produce various microstructures. The resultant tensile strengths ranged from 1217 to 1564 MPa. Both the B-free and B-modified alloys showed almost the same tensile strength when they were subjected to the same heat treatment. When the tensile strength level was below ~1200 MPa, the B-modified alloy showed higher HCF strength compared to the B-free counterpart. In these cases, the fatigue crack originated from grain boundaries. In contrast, when the tensile strength level was above 1250 MPa, the HCF strength of the B-modified alloy was inferior to the B-free counterpart. The fatigue crack initiated neither from the grain boundaries nor from the microstructural unit but rather from the interface between TiB and matrix. In sum, the HCF behavior and the origin of the fatigue crack initiation of a B-modified alloy was highly dependent on its microstructures, and, thus, on its tensile strength including the critical tensile strength level at ~1250 MPa, where deterioration of fatigue strength occurred due to the presence of TiB.
      PubDate: 2021-01-03
       
  • High-Productivity and High-Strength Fe/Al and Al/Al Dissimilar Joining by
           Spot Forge-Welding
    • Abstract: Abstract To realize high-speed and high-strength joining of dissimilar materials that can be used in an automobile manufacturing line, two types of dissimilar lap-joining were examined using spot forge-welding. The material combinations were high-tensile steel SPFC980 × aluminum (Al) alloy AA5083 and Al alloy AA2024 × Al alloy AA6061. The processing time was less than 0.1 second via diffusion bonding with plastic flow. Joint strength depended on the reduction ratio (R), which indicates the degree of plastic flow, and the joints fractured in base metal (BM) at R > 1.8 in the SPFC980 × AA5083 and at R > 1.4 in the AA2024 × AA6061. In each case, the maximum tensile-shear load reached approximately 4 kN. Cross-sections showed metallurgical joining in the forged area. Electron probe microanalysis for elemental oxygen in cross-sections of SPFC980 × AA5083 joints revealed that the contamination layer at the bonded interface decreased with increasing R; formation of new surface by plastic flow occurred better at the forged center than at the edge. Under the R condition for BM fracture, both combinations had suitable solid-state bonding interfaces for dissimilar joining. The reaction layer (RL) at the bonded interface of the SPF980 × AA5083 joint was suppressed to a thickness of several nanometers. No distinct RL formed at the bonded interface of the AA2024 × AA6061 joint; the boundary showed high crystallinity similar to that of the BM grain boundary. These results may facilitate the development of next-generation solid-state spot-welding systems capable of multimaterial manufacturing for transportation vehicles.
      PubDate: 2021-01-02
       
  • Microstructural Evolution and Solute Migration in the Mushy Zone of
           Peritectic Al-18 At. Pct Ni Alloy in High Magnetic Fields
    • Abstract: Abstract The solute migration behavior in the mushy zone of an Al-18 at. pct Ni alloy under a high magnetic field was investigated experimentally. Quenching experiments were carried out under different magnetic fields after thermal stabilization. Directional solidification experiments were conducted to explore the precipitation mechanism. A high magnetic field affected the solute migration in the mushy zone significantly. When exposed to a magnetic field, the original cellular-like peritectic Al3Ni changed into an irregular block shape, with many precipitated small dendritic Al3Ni phases, which have not been observed previously. Directional solidification experiments proved that the dendrite phase precipitated during quenching. The application of a magnetic field resulted in the original straight and clear peritectic interfaces becoming uneven and rugged. A coupling of Lorentz, thermoelectromagnetic, and magnetic forces was proposed to explain solute migration in the mushy zone. This coupling hindered the original solute transport behavior and crystal growth mechanism, induced melting and solidification along the transverse direction, and produced many Ni-rich droplets and concentrated Ni atoms at the peritectic interface during thermal stabilization. This study enriches the influence mechanism of high magnetic fields on the solidification of peritectic alloys and provides the possibility for further microstructure and alloy property regulation.
      PubDate: 2021-01-02
       
  • The Role of HAZ Softening on Cross-Tension Mechanical Performance of
           Martensitic Advanced High Strength Steel Resistance Spot Welds
    • Abstract: Abstract Giga-grade martensitic advanced high-strength steels are prone to sub-critical heat-affected zone (SCHAZ) softening during resistance spot welding. The article aims at understanding the role of HAZ softening on the fracture mode, load-bearing capacity, and energy absorption capability of MS1400 resistance spot welds during the cross-tension test. The highest load-bearing capacity was obtained when pullout failure was initiated from the martensitic coarse-grained HAZ. However, more severe HAZ softening and formation of a wider softened zone, promoted at high heat input conditions, encourages strain localization in SCHAZ, promoting transition in failure location to sub-critical HAZ. This change in pullout failure location is responsible for the observed reduction in the weld peak load at high welding currents. Therefore, control of martensite tempering in the HAZ is critical to obtain strong and reliable resistance spot welds in martensitic advanced high-strength steel sheets. To preclude the detrimental effect of the martensite tempering on the weld strength, the minimum welding current, which enables pullout failure mode, should be used for resistance spot welding of MS1400 advanced martensitic steel.
      PubDate: 2021-01-02
       
  • Effect of Pre-induced Plastic Strains on the Corrosion Behavior of
           Reinforcing Bar in 3.5 pct NaCl Solution
    • Abstract: Abstract Reinforcing steel bar (rebar) is subjected to various levels of strains during service in reinforced concrete (RC) construction. This work aims at understanding the effect of pre-induced plastic strains on the corrosion behavior of a reinforcing steel bar (rebar) by doing electrochemical tests (electrochemical impedance and potentiodynamic polarization) in freely aerated 3.5 pct NaCl solution and cyclic salt-fog test. The interplay between the corrosion products and the corroding tendency of the strained rebars as a function of exposure time is analyzed. The plastic strains have strong effect on the composition of the rusts and polarization resistance of the rusted rebars.
      PubDate: 2021-01-02
       
  • The Anomalous Nucleation in Al-Tb Metallic Glasses
    • Abstract: Abstract The effects of amorphous structure on the devitrification of Al90Tb10 marginal glass former system were investigated in detail by a combined study of high-energy X-ray diffraction (HEXRD), X-ray absorption fine structure (EXAFS), reverse Monte Carlo simulations (RMC), transmission electron microscopy (TEM) and thermal analyses. The atomic structures of melt-spun ribbons and magnetron sputtered amorphous samples with the same composition were simulated using RMC constrained by XRD, EXAFS, and ab-initio results. The fcc-Al nanocrystals nucleated and grown in thin-film specimens have a limited size with almost perfect spherical morphology. The population of these nanocrystals is three orders of magnitude higher as compared to ribbon specimens. The differences in the devitrified ribbon and thin-film metallic glasses were traced back to structural differences in the amorphous state. The amorphous melt-spun ribbons and magnetron sputtered thin- films were found to have different degrees of short-range order and clustering.
      PubDate: 2021-01-02
       
  • Heat Transfer and Materials Flow Modeling of FSW for CuCrZr Alloy Using
           Experimentally Determined Thermo-Physical Properties
    • Abstract: Abstract A three-dimensional heat transfer and material flow-based model using experimentally measured thermo-physical properties has been developed for friction stir welding (FSW) of Cu-0.8Cr-0.1Zr alloy. CuCrZr alloy is a precipitation-hardened copper alloy with good electrical and thermal conductivity and moderate strength at elevated temperatures. The temperature-dependent specific heat, thermal conductivity, and yield strength of the alloy were determined experimentally to develop a reliable and accurate numerical model. The results from numerical model were validated by performing suitable experiments for numerous tool rotational speeds and welding speeds during joining of 3-mm-thick CuCrZr alloy on a dedicated FSW machine. The temperature evolution across the welds was measured using thermocouples. The results from the developed numerical model were validated by comparing it with the measured weld thermal cycles, peak temperatures, and thermo-mechanically-affected zone (TMAZ) for various welds. Validation was also supported with microstructural evidences from the weld nugget zone and TMAZ. The developed model showed the capability to simulate FSW of CuCrZr alloy and predict the important results with reasonably good accuracy
      PubDate: 2021-01-02
       
  • Novel Approach of Electroshock Treatment for Defect Repair in Near- β
           Titanium Alloy Manufactured via Directed Energy Deposition
    • Abstract: Abstract A subsecond and novel approach of electroshock treatment (EST) is used in this study to repair defects in directed-energy-deposited Ti-5Al-5Mo-5V-3Cr-1Zr near-β titanium alloy. After EST, the porosity of the specimen decreased significantly from 0.81 to 0.1 pct. Large cracks observed at the bottom of the above mentioned near-β titanium alloy became intermittent small cracks and the number of voids decreased. The defects in the top and middle regions of the specimens are repaired. The potential defect repair is attributable to energy concentration, which promoted the coalescence of defect tips, and thermal stresses, which compressed the defects inward and closed them.
      PubDate: 2021-01-02
       
 
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