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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

Influence of layer thickness on formation quality,microstructure,mechanical properties,and corrosion resistance of WE43 magnesium alloy fabricated by laser powder bed fusion

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Journal of magnesium and alloys 2024年第4期12卷 1367-1385页

作者： Bangzhao Yin Jinge Liu Bo Peng Mengran Zhou Bingchuan Liu Xiaolin Ma Caimei Wang Peng Wen Yun Tian Yufeng Zheng State Key Laboratory of Tribology in Advanced Equipment Beijing100084China Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China Institute for Precision Medicine Tsinghua UniversityBeijing102218China Department of Orthopaedics Peking University Third HospitalBeijing 100191China Beijing AKEC Medical Co. Ltd.Beijing 102200China School of Materials Science and Engineering Peking UniversityBeijing 100871China Engineering Research Center of Bone and Joint Precision Medicine Ministry of EducationBeijing 100191China

Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.

关键词： magnesium alloy WE43 Laser powder bed fusion Layer thickness Process optimization

On dry machining of AZ31B magnesium alloy using textured cutting tool inserts

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Journal of magnesium and alloys 2024年第4期12卷 1608-1618页

作者： Shailendra Pawanr Kapil Gupta Department of Mechanical and Industrial Engineering Technology University of JohannesburgDoornfontein CampusJohannesburg 2028 South Africa

magnesium alloys have many advantages as lightweight materials for engineering applications,especially in the fields of automotive and aerospace.They undergo extensive cutting or machining while making products out of them.Dry cutting,a sustainable machining method,causes more friction and adhesion at the tool-chip interface.One of the promising solutions to this problem is cutting tool surface texturing,which can reduce tool wear and friction in dry cutting and improve machining performance.This paper aims to investigate the impact of dimple textures(made on the flank face of cutting inserts)on tool wear and chip morphology in the dry machining of AZ31B magnesium alloy.The results show that the cutting speed was the most significant factor affecting tool flank wear,followed by feed rate and cutting depth.The tool wear mechanism was examined using scanning electron microscope(SEM)images and energy dispersive X-ray spectroscopy(EDS)analysis reports,which showed that at low cutting speed,the main wear mechanism was abrasion,while at high speed,it was adhesion.The chips are discontinuous at low cutting speeds,while continuous at high cutting speeds.The dimple textured flank face cutting tools facilitate the dry machining of AZ31B magnesium alloy and contribute to ecological benefits.

关键词： magnesium alloy Dry machining Textured tools Flank wear Sustainability

Effects of orientation on the fatigue crack growth behaviors of the ZK60 magnesium alloy in air and PBS

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Journal of magnesium and alloys 2024年第1期12卷 281-294页

作者： Jiaqi Hu Zheng Liu Zuoliang Ning Hong Gao School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Chemical Process Safety and Equipment Technology Tianjin 300072China

Strong anisotropic corrosion and mechanical properties caused by specimen orientations greatly limit the applications of wrought magnesium alloys.To investigate the influences of specimen orientation,the corrosion tests and(corrosion)fatigue crack growth tests were conducted.The rolled and transverse surfaces of the materials show distinct corrosion rate differences in the stable corrosion stage,but the truth is the opposite for the initial stage of corrosion.In air,specimen orientations have a significant influence on the plastic deformation mechanisms near the crack tip,which results in different fatigue fracture surfaces and cracking paths.Compared with R-T specimens,N-T specimens show a slower fatigue crack growth(FCG)rate in air,which can be attributed to crack closure effects and deformation twinning near the crack tip.The corrosion environment will not significantly change the main plastic deformation mechanisms for the same type of specimen.However,the FCG rate in phosphate buffer saline(PBS)is one order of magnitude higher than that in air,which is caused by the combined effects of hydrogen-induced cracking and anodic dissolution.Owing to the similar corrosion rates at crack tips,the specimens with different orientations display close FCG rates in PBS.

关键词： magnesium alloy Orientation Corrosion Fatigue crack growth

Biomedical rare-earth magnesium alloy:Current status and future prospects

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Journal of magnesium and alloys 2024年第4期12卷 1260-1282页

作者： Mingli Yang Cheng Chen Dongsheng Wang Yinjin Shao Wenhao Zhou Cijun Shuai Youwen Yang Xinghai Ning Institute of Additive Manufacturing Jiangxi University of Science and TechnologyNanchang 330013China Key Laboratory of Construction Hydraulic Robots of Anhui Higher Education Institutes Tongling UniversityTongling 244061China Department of Rehabilitation Ganzhou People’s HospitalGanzhou 341099China Shaanxi Key Laboratory of Biomedical Metallic Materials Northwest Institute for Non-Ferrous Metal ResearchXi’an 710016China State Key Laboratory of High Performance Complex Manufacturing Central South UniversityChangsha 410083China School of Mechanical and Electrical Engineering Jiangxi University of Science and TechnologyGanzhou 341000China College of Engineering and Applied Science Nanjing University210089China

Biomedical magnesium(Mg)alloys have garnered significant attention because of their unique biodegradability,favorable biocompatibility,and suitable mechanical properties.The incorporation of rare earth(RE)elements,with their distinct physical and chemical properties,has greatly contributed to enhancing the mechanical performance,degradation behavior,and biological performance of biomedical Mg alloys.Currently,a series of RE-Mg alloys are being designed and investigated for orthopedic implants and cardiovascular stents,achieving substantial and encouraging research progress.In this work,a comprehensive summary of the state-of-the-art in biomedical RE-Mg alloys is provided.The physiological effects and design standards of RE elements in biomedical Mg alloys are discussed.Particularly,the degradation behavior and mechanical properties,including their underlying action are studied in-depth.Furthermore,the preparation techniques and current application status of RE-Mg alloys are reviewed.Finally,we address the ongoing challenges and propose future prospects to guide the development of high-performance biomedical Mg-RE alloys.

关键词： magnesium alloy Rare earth elements Biodegradation behavior Mechanical performance Biological properties

Gradient microstructure and superior strength-ductility synergy of AZ61 magnesium alloy bars processed by radial forging with different deformation temperatures

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Journal of Materials Science & Technology 2024年第3期170卷 65-77页

作者： Jingfeng Zou Lifeng Ma Yanchun Zhu Ling Qin Yuan Yuan School of Mechanical Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China Heavy Machinery Engineering Research Center of the Ministry Education Taiyuan University of Science and TechnologyTaiyuan 030024China Department of Engineering University of HullCottingham RdHull HU67RXUK National Engineering Research Center for magnesium alloys Chongqing UniversityChongqing 400044China

Gradient microstructure modification is a cost-efficient strategy for high strength without compromising ductility,which is urgently needed in the fundamental science of engineering materials.In this study,heterogeneous structures of AZ61 alloy bars with anisotropic gradients(with different grain size distributions from the surface to the center)were observed to exhibit strong strength-ductility synergies under different deformation tem peratures.The results reveal that the grain refinement process under mediumlow temperature deformation conditions(≤350℃)consists of four transition stages along the radial direction,i.e.,twin activations and deformation band formations,dislocation cells and pile-ups,ultrafine sub-grains,and randomly orientated quasi-micron grains.Different deformation temperatures have a great influence on twin activations and deformation band formations,and the high temperature can easily provoke the initiation of non-basal slip.The deformation bands were determined as a primary nucleation site due to their highly unstable dislocation hindrance ability.Analysis in combination with the Radial forging(RF)deformation process,the differences of dynamic precipitates can be attributed to microstructural difference and solubility limit of Al at different tem peratures.By summarizing the tensile test results,the sample forged at 350℃exhibited the best strength-ductility synergy,exhibiting the highest elongation(EL)of 23.2%with a 251 MPa yield strength(YS)and 394 MPa ultimate tensile strength(UTS)in center region,and combined with the highest strength value of 256 MPa YS and 420 MPa UTS in the center region,while the EL was slightly degraded to 19.8%.

关键词： Gradient microstructure Radial forging Strength-ductility synergy magnesium alloy Strengthening mechanism

Influence of ammonium sulfate on the corrosion behavior of AZ31 magnesium alloy in chloride environment

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Journal of magnesium and alloys 2024年第3期12卷 1082-1101页

作者： Feng Ge Zhongyu Cui Yue Liu Li Lei Xin Wang Hongzhi Cui School of Materials Science and Engineering Ocean University of ChinaQingdao 266100China Beijing National Innovation Institute of Lightweight Ltd.Beijing 101499China

Electrochemical corrosion of AZ31 magnesium alloy in the NH_(4)^(+)-SO_(4)2−-Cl−environment is studied.Effect of NH_(4)^(+)overshadows that of Cl−as the(NH_(4))_(2)SO_(4) concentration is 0.005 M or higher,yielding an evolution from localized corrosion to uniform corrosion.Acceleration effect of NH_(4)^(+)can be attributed to that(i)NH_(4)^(+)dissolves the inner MgO and hinders the precipitation of Mg(OH)_(2) and(ii)the buffering ability of NH_(4)^(+)provides H+,enhances the hydrogen evolution,and expedites the corrosion process.The latter is demonstrated as the dominant factor with the results in unbuffered and buffered environments.The severe corrosion and hydrogen process in NH_(4)^(+)-containing solution results in a high Hads coverage and yields an inductive loop within the low frequency.Meanwhile,SO_(4)^(2−)is helpful in generating cracked but partially protective corrosion products,while Cl−could broaden the corrosion area beneath the corrosion product.

关键词： magnesium alloy Ammonium corrosion Electrochemical kinetic parameter Anodic dissolution.

Microstructure homogeneity and mechanical properties of laser-arc hybrid welded AZ31B magnesium alloy

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Journal of magnesium and alloys 2024年第5期12卷 1986-1995页

作者： Yongkang Gao Kangda Hao Lianyong Xu Yongdian Han Lei Zhao Wenjing Ren Hongyang Jing School of Materials Science and Engineering Tianjin University Tianjin Key Laboratory of Advanced Joining Technology

Laser-arc hybrid welding of AZ31B magnesium alloy was carried out, the effects of welding parameters on weld formation, microstructure homogeneity and mechanical properties were investigated. The results showed that laser-arc hybrid welding was beneficial to improve the weld formation of magnesium alloy by inhibiting the defect of undercut and pores. The weld microstructure was mainly columnar grains neighboring the fusion line and equiaxed grains at the weld center. It was interesting that the grain size at the upper arc zone was smaller than that at the lower laser zone, with the difference mainly affected by laser power rather than welding current and welding speed. The welding parameters were optimized as laser power of 3.5 kW, welding current of 100 A and welding speed of 1.5 m/min. In this case,the weld was free of undercut and pores, and the tensile strength and elongation rate reached 252 MPa and 11.2%, respectively. Finally,the microstructure homogeneity was illustrated according to the heat distribution, and the evolution law of tensile properties was discussed basing on the weld formation and microstructure characteristics.

关键词： magnesium alloy Laser-arc hybrid welding Microstructure homogeneity Mechanical properties

Strengthening effect of prefabrication(10-12) tensile twinning on AZ80+0.4%Ce magnesium alloy and inhibition mechanism of discontinuous precipitation

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Journal of magnesium and alloys 2024年第5期12卷 1918-1930页

作者： Zhen Wang Xi Zhao Zhimin Zhang Yaojin Wu Kai Chen Xianwei Ren Dengkui Wang Wei Wang School of Mechanical and Electrical Engineering North University of China Engineering Technology Research Center for Integrated Precision Forming of Shanxi Province North University of China

This paper provided an effective method to further improve the mechanical properties of the AZ80+0.4%Ce magnesium alloy wheel spoke. The effect of high strength and ductility was obtained with a yield strength of 295.36 MPa, an elongation of 10%, by the combination of pre-deformation(7% deformation) and two-stage aging treatment(120 ℃/9 h + 175 ℃/24 h). The evolution of the microstructure and properties of the alloy was explored under the coupling conditions of different pre-deformation degrees and multi-stage aging. The results show that, pre-deformation introduced a large number of(■) tensile twinning and dislocations, which greatly promoted the probability of continuous precipitates(CPs) appearing. On the contrary, the discontinuous precipitates(DPs) were limited by the vertical and horizontal twin structure. As a result, the pre-nucleation method of two-stage aging increased the proportion of CPs by 34%-38%. Owing to the DPs was effectively suppressed, the alloy's yield strength has been greatly improved. Besides, under multi-stage aging, the twin boundaries induce protruding nucleation to form static recrystallization by hindering the migration of dislocations, and the matrix swallows the twins, then the texture gradually tilts from the two poles to the basal plane. As an important supplement, the grain refinement and oblique texture promoted the improvement of the yield strength of the component.

关键词： magnesium alloy Pre-deformed Two-stage aging Tensile twinning Continuous precipitates Texture

The influence of alternating cyclic dynamic loads with different low frequencies on the bio-corrosion behaviors of AZ31B magnesium alloy in vitro

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Bioactive Materials 2022年第1期7卷 263-274页

作者： Linyuan Han Zhenwei Zhang Jianwei Dai Xuan Li Jing Bai Zhihai Huang Chao Guo Feng Xue Chenglin Chu School of Materials Science and Engineering Southeast UniversityNanjing211189JiangsuChina Jiangsu Key Laboratory for Advanced Metallic Materials Southeast UniversityNanjing211189JiangsuChina School of Materials Engineering Nanjing Institute of TechnologyNanjing211189JiangsuChina Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing211189China

The real physiological environment of human body is complicated with different degrees and forms of dynamic loads applied to implanted medical devices due to the daily activities of the patients,which would have impacts on the degradation behaviors of magnesium alloy implants.In this work,the bio-corrosion behaviors of AZ31B magnesium alloy under alternating cyclic dynamic loads with different low frequencies(0.1-2.5 Hz)were specially investigated.It was found that the bio-degradation performances under external dynamic stressed conditions were much severer than those under unstressed conditions and static loads.The corrosion rates were generally accelerated as the rise of cyclic frequency.Hereby a numerical model for the degradation process of Mg alloy was established.The corrosion current density icorr of Mg alloy and the applied loading frequency f matches a linear relationship of ln icorr∝f,which is the result of interactions between the cyclic alternating load and corrosive environment.This work could provide a theoretical reference and an experimental basis for further researches on the biodegradation behaviors of biomedical materials under dynamic conditions.

关键词： magnesium alloy Biocorrosion Fatigue Frequency