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Journal of magnesium and alloys 2023年第1期11卷 379-391页

作者： Yu Lei Hang Li Yujie Liu Ziyi Wang Guozheng Kang Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu 610031China

The uniaxial ratchetting-fatigue interaction of extruded AZ31 magnesium(Mg)alloy is investigated by uniaxial stress-controlled cyclic tests at room temperature and with addressing the roles of different plastic deformation mechanisms.Different stress levels are prescribed to reflect the cyclic plasticity of the alloy controlled by diverse deformation mechanisms(i.e.,dislocation slipping,deformation twinning and detwinning ones),and then the influences of stress level and stress rate on the ratchetting and fatigue life are discussed.The experimental results demonstrate that different evolution characteristics of whole-life ratchetting and fatigue life presented during cyclic tests with various mean stresses,stress amplitudes and stress rates are determined by the dominated plastic deformation mechanisms.It’s worth noting that the ratchetting can occur in the compressive direction even in the cyclic tests with a positive(tensile)mean stress,and the fatigue life increases first and then decreases with the increase of mean stress on account of the interaction between dislocation slipping and twinning/detwinning mechanisms.Comparing the fatigue lives obtained in the asymmetric stress-controlled and symmetrical strain-controlled cycle tests,it is seen that the ratchetting deformation causes an additional damage,and then leads to a shortening of fatigue life.

关键词： magnesium alloy Ratchetting Low-cycle fatigue Mean stress Stress amplitude Stress rate

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

Recent advances in surface endothelialization of the magnesium alloy stent materials

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Journal of magnesium and alloys 2023年第1期11卷 48-77页

作者： Changjiang Pan Xuhui Liu Qingxiang Hong Jie Chen Yuxin Cheng Qiuyang Zhang Lingjie Meng Juan Dai Zhongmei Yang Lingren Wang Faculty of Mechanical and Material Engineering Jiangsu Provincial Engineering Research Center for Biomaterials and Advanced Medical DevicesHuaiyin Institute of TechnologyHuai’an 223003China The Affiliated Huai’an Hospital of Xuzhou Medical University Huai’an 223003China

magnesium and its alloy have good mechanical properties and biodegradability,and have become the hotspot of the next-generation biodegradable vascular stent materials.However,their rapid degradation in vivo and poor biocompatibility are still the bottlenecks of clinical applications for the cardiovascular stents.In particular,how to induce the repair and regeneration of the vascular endothelial with normal physiological functions on the surface of the magnesium alloy stent materials represents the key to its clinical application in the field of cardiovascular stents.It has been believed that it is an ideal way to completely solve the postoperative complications through constructing the multifunctional anti-corrosive bioactive coating on the magnesium alloy surface to induce the formation of vascular endothelium with normal physiological functions.However,how to construct a corrosion-resistant multifunctional bioactive coating with the good endothelial regeneration abilities on the magnesium alloy surface still faces a great challenge.This paper mainly focused on highlighting and summarizing the recent advances in the surface endothelialization of the magnesium alloy materials for the vascular stent,including the bio-inert coating,in-situ immobilization of bioactive molecules on the surface,polymer coating loaded with bioactive factors,novel multifunctional polymer coating,bioactive micropatterns,bioactive layer with glycocalyx-like structure,NO-releasing coating and bioactive sol-gel coating.The advantages and disadvantages of these strategies were discussed and analyzed.Finally,in the senses of future development and clinical application,this paper analyzed and summarized the development direction and prospect of surface endothelialization of the magnesium alloy vascular stents.It is anticipated that this review can give the new cues to the surface endothelialization of the cardiovascular magnesium alloy stents and promote future advancements in this field.

关键词： magnesium alloy Stent Endothelialization Surface coating Surface modification

Development and characteristics of a low rare-earth containing magnesium alloy with high strength-ductility synergy

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Journal of magnesium and alloys 2023年第5期11卷 1629-1642页

作者： Zijian Yu Xi Xu Kang Shi Baotian Du Xiuzhu Han Tao Xiao Shubo Li Ke Liu Wenbo Du Faculty of Materials and Manufacturing Beijing University of Technology100 PenLe YuanChaoyang DistrictBeijing 100124China Beijing Institute of Spacecraft System Engineering Beijing 100094China

In this study,we successfully developed a low RE containing Mg-3Y-2Gd-1Nd-0.5Zr(wt%)alloy with high strength-ductility synergy by combined processes of hot extrusion,hot rolling and ageing.This alloy exhibits an excellent strength-ductility balance(UTS of 345±2.0 MPa,TYS of 301±5.0 MPa and EL of 9.2±1.9%),which is better than that of many Mg-RE wrought alloys with higher RE concentration and even comparable to that of 6061 Al wrought alloy.A long-range chain-like structure consisting ofβphase,βH phase,βM phase and zig-zag atomic columns is observed for the first time in the studied alloy.The combined process of hot extrusion and hot rolling boosts the formation of deformed grains and low angle grain boundaries,and makes the deformed grains dominate in the alloy strengthening.Under this circumstance,the following ageing generates a novel heterogeneous structure comprising the long-range chain-like structure with broad interparticle spacing and the spacious precipitate-free zones in the deformed grains,which plays a key role in the concurrent strengthening and toughening of the alloy.The present study demonstrates that the deformed grains with long-range chain-like structures and precipitate-free zones is desirable microstructure for the low RE containing Mg alloys to achieve high strength-ductility synergy.

关键词： magnesium alloy Microstructure Mechanical properties Rare earth

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

Preparation and property of self-sealed plasma electrolytic oxide coating on magnesium alloy

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International Journal of Minerals,Metallurgy and Materials 2023年第5期30卷 959-969页

作者： Chen Ma Dong Wang Jinyu Liu Ning Peng Wei Shang Yuqing Wen Guangxi Key Laboratory of Electrochemical and Magnetochemical Function Materials College of Chemistry and BioengineeringGuilin University of TechnologyGuilin 541004China

Plasma electrochemical oxidation (PEO) is a surface modification technology to form ceramic coatings on magnesium alloys However,its application is limited due to its defects.This work reports a novel preparation of in-situ sealing of PEO coatings by four-layer voltage and sol addition.The morphology and structure were characterized by scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDS),and X-ray diffractometer (XRD).Image-Pro Plus 6.0 was used to determine the porosity of the coating,which was decreased from 8.53%to 0.51%.Simultaneously,the coating thickness was increased by a factor of four.The anti-corrosion performance of each sample was evaluated using electrochemical tests,and the findings revealed that the corrosion current density of coatings (i_(corr)) of the samples were lowered from 9.152×10^(-2) to 6.152×10^(-4) mA·cm^(-2),and the total resistance (R_(T)) of the samples were enhanced from 2.19×10^(4) to 2.33×10^(5)Ω·cm^(2).The salt spray test used to simulate the actual environment showed that corrosion points appeared on the surface of the coating only at the 336 h.In addition,the mechanism of PEO self-sealing behavior was described in this article.

关键词： magnesium alloy in-situ sealing plasma electrolytic oxidation corrosion resistance

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

Study on anisotropy of microstructure and mechanical properties of AZ31 magnesium alloy fabricated by wire arc additive manufacturing

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China Foundry 2023年第4期20卷 280-288页

作者： Dong Ma Chun-jie Xu Jun Tian Shang Sui Can Guo Xiang-quan Wu Zhong-ming Zhang School of Materials Science and Engineering Xi'an University of TechnologyXi'an 710048China Xi'an Shechtman Nobel Prize New Materials Institute Xi'an 710048China Xi'an Key Laboratory of Advanced magnesium alloy Additive Manufacturing and Precision Forming Xi'an 710048China MGM Nobel Prize New Materials Co. Ltd.Tongchuan 727100ShaanxiChina

Based on wire arc additive manufacturing(WAAM)technology,AZ31 magnesium alloy in bulk was successfully fabricated,and its microstructure as well as mechanical properties in different planes were observed and analyzed.The AZ31 magnesium alloy has a similar microstructure in the building direction(Z)and travel direction(X),both of which are equiaxed grains.There are heat-affected zones(HAZs)with coarse grains below the fusion line.The second phase is primarily composed of the Mg17Al12 phase,which is evenly distributed in different directions.In addition,the residual stress varies in different directions.There is no significant difference in the hardness of the AZ31 alloy along the Z and X directions,with the average hardness being 68.4 HV and 67.9 HV,respectively.Even though the specimens’ultimate tensile strength along the travel direction is higher in comparison to that along the building direction,their differences in elongation and yield strength are smaller,indicating that the anisotropy of the mechanical properties of the material is small.

关键词： magnesium alloy wire arc additive manufacturing anisotropy microstructure mechanical properties

Mechanism of plasticity enhancement of AZ31B magnesium alloy sheet by accumulative alternating back extrusion

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Journal of magnesium and alloys 2023年第5期11卷 1791-1801页

作者： Ye Wang Feng Li Nan Bian Hua Qiu Du Peng Da Huo School of Materials Science and Engineering Harbin University of Science and TechnologyHarbin 150040PR China Key Laboratory of Advanced Manufacturing and Intelligent Technology Ministry of EducationHarbin University of Science and TechnologyHarbin 150080PR China

Accumulative alternating back extrusion was a potential fine-grain modification method.In this paper,it was an innovative attempt to develop high-performance magnesium alloy sheet by this process.Under the condition of 350 K,commercial AZ31 magnesium alloy was made into billet by accumulative alternating back extrusion,and then extruded into fine-grain magnesium alloy sheet.Through a systematic study of its microstructure and mechanical properties,the results showed that the initial state had an important influence on the evolution of the structure during extrusion.After accumulative alternating back extrusion to produce the billet,the grain size of the sheet obtained by extrusion was significantly refined,which was related to the accumulation of deformation and grain refinement during the alternating loading process.Grain refinement caused the proportion of dynamic recrystallization inside the sheet with 2 cycles of accumulative alternating back extrusion to drop to 27%.With the increase of extrusion cycles from 2 to 4,the high density of dislocations led to an increase in the proportion of dynamic recrystallization and finer grains.The texture changed from strong basal texture to weak bimodal texture.The results of uniaxial tensile test show that due to grain refinement and texture change,the yield strength was significantly reduced,and the plasticity was significantly improved.It was verified that accumulative alternating back extrusion was meaningful for subsequent processing,and it also provided scientific guidance for the development of fine-grained magnesium alloy sheet.

关键词： magnesium alloy Alternating back extrusion Microstructure uniformity Bimodal texture Texture weakening Sheet anisotropy

Generating micro/nanostructures on magnesium alloy surface using ultraprecision diamond surface texturing process

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Journal of magnesium and alloys 2023年第4期11卷 1472-1483页

作者： Hanheng Du Mengnan Jiang Zuankai Wang Zhiwei Zhu Suet To State Key Laboratory of Ultra-Precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHong KongChina Department of Mechanical Engineering City University of Hong KongHong KongChina School of Mechanical Engineering Nanjing University of Science and TechnologyNanjingChina

The lightness and high strength-to-weight ratio of the magnesium alloy have attracted more interest in various applications.However,micro/nanostructure generation on their surfaces remains a challenge due to the flammability and ignition.Motivated by this,this study proposed a machining process,named the ultraprecision diamond surface texturing process,to machine the micro/nanostructures on magnesium alloy surfaces.Experimental results showed the various microstructures and sawtooth-shaped nanostructures were successfully generated on the AZ31B magnesium alloy surfaces,demonstrating the effectiveness of this proposed machining process.Furthermore,sawtooth-shaped nanostructures had the function of inducing the optical effect and generating different colors on workpiece surfaces.The colorful letter and colorful flower image were clearly viewed on magnesium alloy surfaces.The corresponding cutting force,chip morphology,and tool wear were systematically investigated to understand the machining mechanism of micro/nanostructures on magnesium alloy surfaces.The proposed machining process can further improve the performances of the magnesium alloy and extend its functions to other fields,such as optics.

关键词： magnesium alloy Micro/nanostructure Ultraprecision diamond surface texturing Cutting force Chip morphology Structural color