Journal of Materials Science & Technology

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ISSN / EISSN : 1005-0302 / 1941-1162
Published by: Elsevier BV (10.1016)
Total articles ≅ 3,725
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S.Y. Wang, , C.Y. Cui, X.F. Sun, , Y.M. Ma, H.L. An
Journal of Materials Science & Technology, Volume 80, pp 244-258; doi:10.1016/j.jmst.2020.05.078

Post-bond heat treatment (PBHT) applied to a transient liquid phase (TLP) bonding joint is an effective approach to remove the brittle borides and improve its properties. Herein, we proposed two types of PBHT strategies to obtain a TLP bonded γ′-strengthened Co-based single crystal superalloy, and the microstructural characteristics and tensile properties of the two heat treated joints were compared to identify the optimal PBHT strategy. The evolution of the brittle boride in the joint after the PBHT was studied by using in-situ microscopy. The experimental results allowed to provide a theoretic model to quantitatively evaluate the distribution of the brittle phase after the optimal PBHT and analyze the joint fractures to understand the failure mechanisms. The obtained results revealed that a post-bond solid solution treatment performed to the joint at a high temperature (over 1275 °C) could decrease the area fraction of the boride from 7.2 % to 1.4 % and increase the elongation from 1.9 % to 7.8 %. This work emphasizes the relevance of solid solution temperature when a PBHT strategy is applied.
Yu Fu, Jun Li, , , Xiaogang Li
Journal of Materials Science & Technology, Volume 80, pp 217-233; doi:10.1016/j.jmst.2020.11.044

In the past decade, the sudden rise of high-entropy alloys (HEAs) has become a research hotspot in the domain of metal materials. HEAs break through the design concept of traditional single-principal element alloys, and the four core effects, especially the high entropy and cocktail effects, make HEAs exhibit much better corrosion resistance than traditional corrosion-resistant metal materials, e.g., stainless steels, copper-nickel alloys, and high-nickel alloys. Currently, the corrosion resistance of HEAs causes great concern in the field of corrosion research. This article reviews the corrosion behavior and mechanism of HEAs in various aqueous solutions, revealing the correlation among the composition, microstructure and corrosion resistance of HEAs, and elaborates the influence of heat treatment, anodizing treatment and preparation methods on the corrosion behavior of HEAs. This knowledge will benefit the on-demand design of corrosion-resistant HEAs, which is an important trend of future development. Finally, perspectives regarding the corrosion research of HEAs are outlined to guide future studies.
Liang-Liang Zhang, Lin-Jie Zhang, Jian Long, Xiang-Dong Ding, Jun Sun, Yuan-Jun Sun
Journal of Materials Science & Technology, Volume 80, pp 1-12; doi:10.1016/j.jmst.2020.06.056

Molybdenum (Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry; however, the embrittlement of welded Mo joints limits its further application. In this study, the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone (FZ) during laser welding. In the FZ of the Mo joints, carbon mainly existed as Mo2C, and some free C atoms, and MoC and MoOxCy phases were also present. The distribution of Mo2C directly influenced the bonding strength of the grain boundaries. As Mo2C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo, it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength. However, the Mo2C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate, thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength. The emergence of the MoOxCy phase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.
Jian Han, Xiaonan Tang, Shaofan Ge, Ying Shi, Chengzhi Zhang, ,
Journal of Materials Science & Technology, Volume 80, pp 259-265; doi:10.1016/j.jmst.2020.11.054

Silicon is considered as one of the most promising anodes for Li-ion batteries (LIBs), but it is limited for commercial applications by the critical issue of large volume expansion during the lithiation. In this work, the structure of silicon/carbon (Si/C) particles on graphene sheets (Si/C–G) was obtained to solve the issue by using the void space of Si/C particles and graphene. Si/C–G material was from Si/PDA-GO that silicon particles was coated by polydopamine (PDA) and reacted with oxide graphene (GO). The Si/C–G material have good cycling performance as the stability of the structure during the lithiation/dislithiation. The Si/C–G anode materials exhibited high reversible capacity of 1910.5 mA h g−1 and 1196.1 mA h g−1 after 700 cycles at 357.9 mA g−1, and have good rate property of 507.2 mA h g−1 at high current density, showing significantly improved commercial viability of silicon electrodes in high-energy-density LIBs.
Zhen Li, , Hai-Jun Zhang, Hua-Fang Li, ,
Journal of Materials Science & Technology, Volume 80, pp 50-65; doi:10.1016/j.jmst.2020.10.076

In order to improve mechanical and corrosion properties of biodegradable pure Zn, a knowledge-based microstructure design is performed on Zn-Li alloy system composed of hard β-LiZn4 and soft Zn phases. Precipitation and multi-modal grain structure are designed to toughen β-LiZn4 while strengthen Zn, resulting in high strength and high ductility for both the phases. Needle-like secondary Zn precipitates form in β-LiZn4, while fine-scale networks of string-like β-LiZn4 precipitates form in Zn with a tri-modal grain structure. As a result, near-eutectic Zn-0.48Li alloy with an outstanding combination of high strength and high ductility has been fabricated through hot-warm rolling, a novel fabrication process to realize the microstructure design. The as-rolled alloy has yield strength (YS) of 246 MPa, the ultimate tensile strength (UTS) of 395 MPa and elongation to failure (EL) of 47 %. Immersion test in simulated body fluid (SBF) for 30 days reveals that Li-rich products form preferentially at initial stage, followed by Zn-rich products with prolonged time. Aqueous insoluble Li2CO3 forms a protective passivation film on the alloy surface, which suppresses the average corrosion rate from 81.2 μm/year at day one down dramatically to 18.2 μm/year at day five. Afterwards, the average corrosion rate increases slightly with decrease of Li2CO3 content, which undulates around the clinical requirements on corrosion resistance (i.e., 20 μm/year) claimed for biodegradable metal stents.
Chang Feng, , , Mengmeng Sun, Jing Tian, Guiying Lu, Li Ma, Xiangbo Li, Jian Hou
Journal of Materials Science & Technology, Volume 80, pp 75-83; doi:10.1016/j.jmst.2020.11.047

The electron mediator can effectively improve the performance of the direct Z-scheme heterojunction photocatalysts. However, it is still a great challenge to select cheap and efficient electron mediators and to design them into the Z-scheme photocatalytic system. In the present paper, the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst was prepared using carbon nanotubes (CNTs) as the electron mediators, and its photocatalytic hydrogen production performance was studied. Compared with single-phase g-C3N4, CdZnS and biphasic g-C3N4/CdZnS photocatalysts, the photocatalytic hydrogen production performance of the prepared g-C3N4/CNTs/CdZnS has been significantly enhanced. Meanwhile, g-C3N4/CNTs/CdZnS possesses very good photocatalytic hydrogen production stability. The enhanced photocatalytic hydrogen production performance of g-C3N4/CNTs/CdZnS is attributed to the fact that CNTs, as an electron mediator, can accelerate the recombination of the photogenerated holes in the valence band of g-C3N4 and the photogenerated electrons in the conduction band of CdZnS, which makes the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst be easier to escape the photogenerated electrons, increases the concentration of the photogenerated carriers and prolongs the lifetime of the photogenerated carriers. This work provides a theoretical basis for the further development and design of CNTs as the intermediate electron mediator of the Z-scheme heterojunction photocatalyst.
Ruiqing Lu, Shuwei Zheng, , Jiamin Hu, Dingfa Fu, Jianchun Chen, Guodong Zhao, , Hui Zhang
Journal of Materials Science & Technology, Volume 80, pp 150-162; doi:10.1016/j.jmst.2020.11.055

In the present work, a double-pass continuous expansion extrusion forming (CEEF) process was proposed for an Al-Mg-Si alloy, in which the diameter of rods was gradually expanded. The microstructural evolution, mechanical properties and deformation characteristics were investigated by utilizing microstructural observations, mechanical testing and a finite element method coupled with a cellular automata model. The results showed that the strength and ductility of the double-pass CEEF processed Al-Mg-Si alloys were improved synchronously, especially in artificially aged alloys. The grain size of the processed Al-Mg-Si alloy rods was refined remarkably by continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), and the homogeneity of microstructure was gradually improved with increasing number of processing passes. The artificially aged alloy processed with double-pass CEEF and water quenching contained fine (sub)grains and high-density dislocations, which resulted in more needle-shaped β” precipitates and a larger precipitate aspect ratio than the as-received and air-cooled CEEF alloys owing to the different precipitation kinetics. The severe cumulate strain and microshear bands were found to accelerate CDRX and GDRX for grain refinement between adjacent positions of the parabolic metal flow due to the special temperature characteristics and large shear straining during the CEEF process.
Tian Wan, Kangjie Chu, Ju Fang, Chuanxin Zhong, Yiwen Zhang, Xiang Ge, Yonghui Ding,
Journal of Materials Science & Technology, Volume 80, pp 266-278; doi:10.1016/j.jmst.2020.11.049

Refractory metal niobium (Nb) incorporated with a small amount of silver (Ag), the resulting Nb-Ag two-phase alloys, were fabricated by mechanical alloying and spark plasma sintering. The microstructure, mechanical properties, wear resistance, corrosion behavior, in vitro and in vivo antibacterial properties and biocompatibility of the Nb-Ag alloys were systematically investigated. The results show that the mechanical properties, wear resistance, corrosion resistance and antibacterial ability were significantly enhanced after addition of 5 at.% Ag. The fabricated Nb-5 at.% Ag alloy demonstrates high yield strength of up to ∼ 1486 MPa and fracture strain of ∼ 35 %. The precipitated Ag particles could reduce friction and wear. The enhanced corrosion resistance was attributed to the higher relative density of the sintered alloys and the formation of a stable and dense passive film of niobium and silver oxides. In vitro and in vivo evaluations show that the Nb-5 at.% Ag alloy also has strong antibacterial activity and good biocompatibility and osteointegration ability. These results demonstrate great potential of the nanostructured Nb-Ag alloys for dental and orthopedic implants.
Zhibiao Yang, , , Zijian Gu, , , Levente Vitos
Journal of Materials Science & Technology, Volume 80, pp 66-74; doi:10.1016/j.jmst.2020.10.078

In order to efficiently explore the nearly infinite composition space in multicomponent solid solution alloys for reaching higher mechanical performance, it is important to establish predictive design strategies using computation-aided methods. Here, using ab initio calculations we systematically study the effects of magnetism and chemical composition on the generalized stacking fault energy surface (γ-surface) of Cr-Co-Ni medium entropy alloys and show that both chemistry and the coupled magnetic state strongly affect the γ-surface, consequently, the primary deformation modes. The relations among various stable and unstable stacking fault energies are revealed and discussed. The present findings are useful for studying the deformation behaviors of Cr-Co-Ni alloys and facilitate a density functional theory based design of transformation-induced plasticity and twinning-induced plasticity mechanisms in Cr-Co-Ni alloys.
Jun Guo, Yu-Ke Zhu, Lin Chen, Zi-Yuan Wang, ,
Journal of Materials Science & Technology; doi:10.1016/j.jmst.2021.05.057

Bi2S3-based alloys are considered promising thermoelectric materials due to their large Seebeck coefficient and low lattice thermal conductivity. However, low electrical conductivity usually leads to poor electrical transport properties, which seriously restricts their further application in thermoelectric refrigeration and/or power generation. In this work, Bi2S3 with high electrical transport properties is synthesized hydrothermally via Se and Cl co-doping. The maximum electrical conductivity value of 483 S cm−1 was obtained for the Bi2S2.4Se0.4Cl0.20 sample at room temperature. The significant improvement of electrical conductivity gives rise to a high average power factor of 411 μW m−1 K−2 during the measuring temperature range and a peak value of 456 μW m−1 K−2 at 673 K. Benefiting from the largely improved electrical transport properties, a superior ZT value of approximately 0.66 and ZTave. of 0.36 were obtained for Bi2S2.4Se0.4Cl0.20, and the theoretically calculated conversion efficiency reached 5.7%. The results indicate that Bi2S3 is a promising candidate for thermoelectric applications at medium temperatures.
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