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Journal of Wuhan University of Technology(materials Science) 2024年第2期39卷 320-326页

作者：李涛凌帅 ZHONG Shujie LOU Qiongyue department of materials engineering School of Mechanical EngineeringChengdu UniversityChengdu 610106China

Ni^(2+)/Cu^(2+)/SO_(4)^(2-)/polyvinyl alcohol precursor fibers with uniform diameters were prepared through electrospinning.Nickel-based composite nanoalloys containing Ni,Cu,and S were prepared through heat treatment in an Ar atmosphere.The experimental results show that the main components of the prepared nanoalloys are NiCu,Ni_(3)S_(2),Ni,and C.The nanoalloys exhibit fine grain sizes about 200-500 nm,which can increase with increasing heat treatment temperature.Electrochemical test results show that the nickel sulfidemodified NiCu nanoalloy composites exhibit excellent oxygen evolution reaction properties,and the oxygen evolution reaction properties gradually improve with the increasing heat treatment temperature.The sample prepared at 1 000℃ for 40 min show a low overpotential of 423 mV and a small Tafel slope of 134 mV·dec^(-1) at a current density of 10 mA·cm^(-2).

关键词： NiCu nanoalloy Ni_(3)S_(2) structure transformation oxygen evolution reaction

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Applying the Protective Mn-Co-La_(2)O_(3)Coating on Crofer 22 APU Ferritic Stainless Steel Used as Solid Oxide Fuel Cell Interconnects

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Acta Metallurgica Sinica(English Letters) 2024年第5期37卷 872-888页

作者： Farhad Mohsenifar Hadi Ebrahimifar Ahmad Irannejad department of materials engineering and Metallurgy Faculty of EngineeringShahid Bahonar University of KermanKermanIran mechanical engineering department Faculty of EngineeringHigher Education Complex of Bam76615-314BamIran department of materials engineering Faculty of Mechanical and Materials EngineeringGraduate University of Advanced TechnologyKerman ***Iran

This research studies the effect of Mn-Co-La_(2)O_(3) coating synthesized by the electrodeposition method on the oxidation resistance and electrical conductivity of the Crofer 22 APU stainless steel interconnect plates in solid oxide fuel cells.The test samples were characterized by a field emission scanning electron microscope(FESEM)equipped with energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The oxidation kinetics of the coated and uncoated samples were studied by tracking their weight changes over time at 800°C,showing that the oxidation mechanism for all samples follows the parabolic law.Lower oxidation rate constant(k_(p))values of the coated sample compared with that of the uncoated one indicated a reduction in the oxidation rate of the steel substrate in the presence of the Mn-Co-La_(2)O_(3) coating.The examination of the cross-section of different samples after the isothermal oxidation for 500 h at 800°C exhibited that applying the composite coating leads to a decrease in the thickness of the chromia layer formed on the steel surface.Furthermore,under these conditions,the area-specific resistance(ASR)of the coated sample(13.11 mΩcm^(2))is significantly lower than that of the uncoated one(41.45 mΩcm^(2)).

关键词： Area specific resistance Oxidation Fuel cell Composite coating

Precipitation kinetics and strengthening of M23C6 in novel G115 martensitic steel:Utilizing secondary normalizing

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Progress in Natural Science:materials International 2024年第2期34卷 396-407页

作者： Chengxian Zhang Zhi Yuan Qiuzhi Gao Qingshuang Ma Hailian Zhang Jing Bai Huijie Zhang Liming Yu Huijun Li School of materials Science and engineering Northeastern University School of Resources and materials Northeastern University at Qinhuangdao School of materials Science & engineering Tianjin University School of mechanical Materials and Mechatronic Engineering University of Wollongong

G115 martensitic steel is anticipated to be one of the preferred candidate materials in ultra-super critical(USC)power plants with steam temperatures above 650℃.Microstructure evolutions and mechanical properties of G115 martensitic steel after applying various heat treatment processes were investigated.The results demonstrate that the main precipitate in G115 martensitic steel after applying various heat treatment processes is M23C6 phase with Cr enrichment.The time required for M23C6 phase precipitation decreases with increasing secondary normalizing temperature and the extension in holding time according to its precipitation-temperature-time(PTT)curves.Volume fraction of M23C6 phase increases with increasing secondary normalizing temperature and holding time,which strengthens the inhibitory effect of precipitates on dislocations recovery and laths growth.Therefore,G115 martensitic steel can obtain the best mechanical properties after applying the highest secondary normalizing temperature and the longest holding time.In the current work,the excellent strength of G115 martensitic steel mainly derives from precipitates strengthening and laths strengthening.

关键词： G115 martensitic steel M23C6 phase Precipitation kinetics Secondary normalizing Strengthening mechanisms

Quantification of grain boundary effects on the geometrically necessary dislocation density evolution and strain hardening of polycrystalline Mg-4Al using in situ tensile testing in scanning electron microscope and HR-EBSD

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Journal of Magnesium and Alloys 2024年第5期12卷 1815-1829页

作者： Eunji Song Mohsen Taheri Andani Amit Misra department of materials Science and engineering University of Michigan department of mechanical engineering University of Michigan

In situ tensile testing in a scanning electron microscope(SEM) in conjunction with high-resolution electron backscatter diffraction(HR-EBSD) under load was used to characterize the evolution of geometrically necessary dislocation(GND) densities at individual grain boundaries as a function of applied strain in a polycrystalline Mg-4Al alloy. The increase in GND density was investigated at plastic strains of 0 %,0.6 %, 2.2 %, 3.3 % from the area including 76 grains and correlated with(i) geometric compatibility between slip systems across grain boundaries, and(ii) plastic incompatibility. We develop expressions for the grain boundary GND density evolution as a function of plastic strain and plastic incompatibility, from which uniaxial tensile stress-strain response of polycrystalline Mg-4Al are computed and compared with experimental measurement. The findings in this study contribute to understanding the mechanisms governing the strain hardening response of single-phase polycrystalline alloys and more reliable prediction of mechanical behaviors in diverse microstructures.

关键词： Mg Al alloys Grain boundaries Geometrically necessary dislocations Strain gradient plasticity HR-EBSD

Modeling asymmetric fracture mechanics of Mg alloy wire in drawing process

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Journal of Magnesium and Alloys 2024年第5期12卷 2057-2069页

作者： Sunghoon Choi Jongwon Shin Joung Sik Suh Dongchoul Kim department of mechanical engineering Sogang University Advanced Metals Division Korea Institute of Materials Science

In this study, a numerical analysis was conducted on the ductile fracture of a 2-mm diameter Mg-1Zn-0.5Mn-0.5Sr-0.1Ca alloy wire during drawing. The hexagonally close-packed crystal structure of Mg alloys causes asymmetric fracture behavior, especially in the compression region. The aim of this study is to develop a comprehensive damage model for Mg alloy wire that accurately predicts ductile fracture, with a focus on the compression region. A novel experimental method was introduced to measure the ductile fracture of Mg alloy wires under different stress states. The wire drawing process was simulated using the Generalized Incremental Stress-State dependent damage(GISSMO)Model and the Semi-Analytical Model for Polymers(SAMP) model. The damage model's prediction and the experimental results were found to be in excellent agreement, especially in determining crack initiation. Computational analysis established a safe zone diagram for die angle and reduction ratio, and experimental validation confirmed the feasibility of this approach. The proposed damage model can provide a practical and reliable analysis for optimizing the drawing process of Mg alloy wire.

关键词： Mg alloy Wire drawing Finite element method Damage model Safe zone diagram

Challenges and opportunities in the production of magnesium parts by directed energy deposition processes

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Journal of Magnesium and Alloys 2024年第5期12卷 1663-1686页

作者： Gürel ?am Ali Günen Iskenderun Technical University Faculty of Engineering and Natural Sciences Department of Mechanical Engineering Iskenderun Technical University Faculty of Engineering and Natural Sciences Department of Metallurgy and Materials Engineering

Mg-alloys have gained considerable attention in recent years for their outstanding properties such as lightweight, high specific strength,and corrosion resistance, making them attractive for applications in medical, aerospace, automotive, and other transport industries. However,their widespread application is hindered by their low formability at room temperature due to limited slip systems. Cast Mg-alloys have low mechanical properties due to the presence of casting defects such as porosity and anisotropy in addition to the high scrap. While casting methods benefit from established process optimization techniques for these problems, additive manufacturing methods are increasingly replacing casting methods in Mg alloys as they provide more precise control over the microstructure and allow specific grain orientations,potentially enabling easier optimization of anisotropy properties in certain applications.Although metal additive manufacturing(MAM) technology also results in some manufacturing defects such as inhomogeneous microstructural evolution and porosity and additively manufactured Mg alloy parts exhibit lower properties than the wrought parts, they in general exhibit superior properties than the cast counterparts. Thus, MAM is a promising technique to produce Mg alloy parts. Directed energy deposition processes, particularly wire arc directed energy deposition(WA-DED), have emerged as an advantageous additive manufacturing(AM) technique for metallic materials including magnesium alloys, offering advantages such as high deposition rates, improved material efficiency, and reduced production costs compared to subtractive processes. However, the inherent challenges associated with magnesium,such as its high reactivity and susceptibility to oxidation, pose unique hurdles in the application of this technology.This review paper delves into the progress made in the application of DED technology to Mg-alloys, its challenges, and prospects.Furthermore, the predominant imperfections, notably inhomogeneous microstructur

关键词： Additive manufacturing DED processes Arc-DED Wire arc additive manufacturing (WAAM) 3-D printing High deposition rate

Numerical simulation on the multiphase flow and reoxidation of the molten steel in a two-strand tundish during ladle change

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International Journal of Minerals,Metallurgy and materials 2024年第7期31卷 1540-1553页

作者： Jingcheng Wang Zhentong Liu Wei Chen Hongliang Chen Lifeng Zhang School of mechanical engineering Yanshan UniversityQinhuangdao 066004China School of materials Science and engineering Tianjin UniversityTianjin 300350China School of mechanical and materials engineering North China University of TechnologyBeijing 100144China

A 3D mathematical model was proposed to investigate the molten steel–slag–air multiphase flow in a two-strand slab continuous casting(CC)tundish during ladle change.The study focused on the exposure of the molten steel and the subsequent reoxidation occurrence.The exposure of the molten steel was calculated using the coupled realizable k–εmodel and volume of fluid(VOF)model.The diffusion of dissolved oxygen was determined by solving the user-defined scalar(UDS)equation.Moreover,the user-defined function(UDF)was used to describe the source term in the UDS equation and determine the oxidation rate and oxidation position.The effect of the refilling speed on the molten steel exposure and dissolved oxygen content was also discussed.Increasing the refilling speed during ladle change reduced the refilling time and the exposure duration of the molten steel.However,the elevated refilling speed enlarged the slag eyes and increased the average dissolved oxygen content within the tundish,thereby exacerbating the reoxidation phenomenon.In addition,the time required for the molten steel with a high dissolved oxygen content to exit the tundish varied with the refilling speed.When the inlet speed was 3.0 m·s^(-1)during ladle change,the molten steel with a high dissolved oxygen content exited the outlet in a short period,reaching a maximum dissolved oxygen content of 0.000525wt%.Conversely,when the inlet speed was 1.8 m·s^(-1),the maximum dissolved oxygen content was 0.000382wt%.The refilling speed during the ladle change process must be appropriately decreased to minimize reoxidation effects and enhance the steel product quality.

关键词： tundish ladle change reoxidation multiphase flow numerical simulation

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Dynamic recrystallization mechanism, texture evolution development and mechanical characteristics of a Mg–8.7Gd–4.18Y–0.42Zr magnesium alloy by ECAP

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Progress in Natural Science:materials International 2024年第2期34卷 376-388页

作者： Ling Zhang Yinglong Li School of materials Science and engineering Northeastern University School of mechanical and engineering Ningxia Institute of Science and Technology

Equal channel angle pressing is recognized for its ability to refine alloy grains and alter grain orientation, thereby achieve better mechanical performance of the magnesium alloy. This study investigates the microstructures,dynamic recrystallization mechanism, texture development, and mechanical performance of GW94K(Mg–8.7Gd–4.18Y–0.42Zr wt. %) Mg alloy following ECAP-4 passes at 400°C and 3 mm/min. Results show that when high-temperature deformation is undertaken, twin formation is suppressed while dislocation slip is facilitated, increasing dislocation density during deformation. Following ECAP deformation, the sample displayed higher fracture elongation, TYS, and UTS than the as-solutioned GW94K alloy. In particular, the GW94K alloy performed well mechanically after ECAP-4 passes, with an ultimate TYS of 231 MPa, an UTS of 290 MPa, and an elongation of 14.8 %. DDRX and shear bands induce CDRX, both of which are important in plastic deformation. as well as in modifying microstructure and grain orientation during ECAP deformation.

关键词： Dynamic recrystallization mechanism Equal channel angular pressing Magnesium alloy mechanical performance Mg-Gd-Y-Zr alloy Texture development

Room and cryogenic deformation behavior of AZ61 and AZ61-xCaO(x = 0.5, 1 wt.%) alloy

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Journal of Magnesium and Alloys 2024年第5期12卷 1996-2009页

作者： Umer Masood Chaudry Hafiz Muhammad Rehan Tariq Nooruddin Ansari Soo Yeol Lee Tea-Sung Jun department of mechanical engineering Incheon National University Research Institute for engineering and Technology Incheon National University department of materials Science&engineering Chungnam National University

This study investigates the influence of CaO(0.5, 1(wt.%)) alloying on the microstructural evolution, texture development and deformation behavior of AZ61 magnesium alloy. The uniaxial tension tests at room(RT) and cryogenic(CT,-150 ℃) temperature were performed to investigate the twinability and dislocation behavior and its consequent effect on flow stress, ductility and strain hardening rate. The results showed that the AZ61-1CaO exhibited superior strength/ductility synergy at RT with a yield strength(YS) of 223 MPa and a ductility of 23% as compared to AZ61(178 MPa, 18.5%) and AZ61-0.5CaO(198 MPa, 21%). Similar trend was witnessed for all the samples during CT deformation, where increase in the YS and decrease in ductility were observed. The Mtex tools based in-grain misorientation axis(IGMA) analysis of RT deformed samples revealed the higher activities of prismaticslip in AZ61-CaO, which led to superior ductility.Moreover, subsequent EBSD analysis of CT deformed samples showed the increased fraction of fine {10-12} tension twins and nucleation of multiple {10-12} twin variants caused by higher local stress concentration at the grain boundaries, which imposed the strengthening by twin-twin interaction. Lastly, the detailed investigations on strengthening contributors showed that the dislocation strengthening has the highest contribution towards strength in all samples.

关键词： Magnesium Twinning Twinning variant EBSD Cryogenic deformation

Negative enthalpy alloys and local chemical ordering:a concept and route leading to synergy of strength and ductility

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National Science Review 2024年第4期11卷 172-184页

作者： Zibing An Tao Yang Caijuan Shi Shengcheng Mao Lihua Wang Ang Li Wei Li Xianmeng Xue Ming Sun Yifan Bai Yapeng He Fuzeng Ren Zhouguang Lu Ming Yan Yang Ren Chain-Tsuan Liu Ze Zhang Xiaodong Han Beijing Key Lab of Microstructure and Property of Advanced materials College of Materials Science &Engineering Beijing University of Technology department of materials Science and engineering City University of Hong Kong Key Laboratory of Partial Acceleration Physics& Technology Institute of High Energy PhysicsChinese Academy of Sciences department of materials Science &engineering Southern University of Science and Technology department of Physics City University of Hong Kong State Key Laboratory of Silicon materials Department of Materials Science and Engineering Zhejiang University

Solid solutions are ubiquitous in metals and alloys. Local chemical ordering(LCO) is a fundamental sub-nano/nanoscale process that occurs in many solid solutions and can be used as a microstructure to optimize strength and ductility. However, the formation of LCO has not been fully elucidated, let alone how to provide efficient routes for designing LCO to achieve synergistic effects on both superb strength and ductility. Herein, we propose the formation and control of LCO in negative enthalpy alloys. With engineering negative enthalpy in solid solutions, genetic LCO components are formed in negative enthalpy refractory high-entropy alloys(RHEAs). In contrast to conventional ‘trial-and-error' approaches, the control of LCO by using engineering negative enthalpy in RHEAs is instructive and results in superior strength(1160 MPa) and uniform ductility(24.5%) under tension at ambient temperature, which are among the best reported so far. LCO can promote dislocation cross-slip, enhancing the interaction between dislocations and their accumulation at large tensile strains; sustainable strain hardening can thereby be attained to ensure high ductility of the alloy. This work paves the way for new research fields on negative enthalpy solid solutions and alloys for the synergy of strength and ductility as well as new functions.

关键词： negative enthalpy alloys local chemical ordering strength ductility dislocation