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Toward understanding the microstructure characteristics,phase selection and magnetic properties of laser additive manufactured Nd-Fe-B permanent magnets

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International Journal of Extreme manufacturing 2024年第1期6卷 277-294页

作者： Bo Yao Nan Kang Xiangyu Li Dou Li Mohamed EL Mansori Jing Chen Haiou Yang Hua Tan Xin Lin State Key laboratory of Solidiffcation Processing Northwestern Polytechnical UniversityXi’anShaanxi 710072People’s Republic of China Arts et Metiers Institute of Technology MSMPHESAM UniversitéF-51006 Chˆalons-en-ChampagneFrance Key laboratory of metal High Performance additive manufacturing and innovative design MIIT ChinaNorthwestern Polytechnical UniversityXi’anShaanxi 710072People’s Republic of China Texas A&M Engineering Experiment Station Institute for Manufacturing SystemsCollege StationTX 77843United States of America

Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infuenced by the phase characteristics and microstructure.In this work,Nd-Fe-B magnets were manufactured using vacuum induction melting(VIM),laser directed energy deposition(LDED)and laser powder bed fusion(LPBF)technologies.Themicrostructure evolution and phase selection of Nd-Fe-B magnets were then clarified in detail.The results indicated that the solidification velocity(V)and cooling rate(R)are key factors in the phase selection.In terms of the VIM-casting Nd-Fe-B magnet,a large volume fraction of theα-Fe soft magnetic phase(39.7 vol.%)and Nd2Fe17Bxmetastable phase(34.7 vol.%)areformed due to the low R(2.3×10-1?C s-1),whereas only a minor fraction of the Nd2Fe14B hard magnetic phase(5.15 vol.%)is presented.For the LDED-processed Nd-Fe-B deposit,although the Nd2Fe14B hard magnetic phase also had a low value(3.4 vol.%)as the values of V(10-2m s-1)and R(1.45×106?C s-1)in the LPBF process resulted in the substantial formation of the Nd2Fe14B hard magnetic phase(55.8 vol.%)directly from the liquid,while theα-Fe soft magnetic phase and Nd2Fe17Bxmetastable phase precipitation are suppressed in the LPBF-processed Nd-Fe-B magnet.Additionally,crystallographic texture analysis reveals that the LPBF-processedNd-Fe-B magnets exhibit isotropic magnetic characteristics.Consequently,the LPBF-processed Nd-Fe-B deposit,exhibiting a coercivity of 656 k A m-1,remanence of 0.79 T and maximum energy product of 71.5 k J m-3,achieved an acceptable magnetic performance,comparable to other additive manufacturing

关键词： laser additive manufacturing(LAM) Nd-Fe-B permanent magnets numerical simulation microstructure magnetic properties

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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

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Shape preserving topology optimization for structural radar cross section control

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Chinese Journal of Aeronautics 2022年第6期35卷 198-210页

作者： Fei CHEN Jihong ZHU Xinxin DU Ruitong ZHANG Weihong ZHANG State IJR Center of Aerospace design and additive manufacturing Northwestern Polytechnical UniversityXi’an 710072China miit Lab of metal additive manufacturing and innovative design Northwestern Polytechnical UniversityXi’an 710072China

The purpose of this paper is to present a shape preserving topology optimization method to prevent the adverse effects of the mechanical deformation on the Radar Cross Section(RCS).The optimization will suppress the variation of RCS on the perfect conductor surface by structural design.On the one hand,the physical optics method is utilized to calculate the structural RCS,which is based on the surface displacement field obtained from the finite element analysis of the structure.The corresponding design sensitivities of topology optimization are derived analytically and solved by the adjoint method.On the other hand,the RCS variation and mechanical performance are taken into account simultaneously by extending a standard compliance-based topology optimization model.Two optimization formulations are discussed in an illustrative example,where the influences of upper limits of the compliance and the RCS variation are considered.Two more examples are further tested to show the ability and validity of the proposed optimization method.

关键词： Adjoint method Physical optics method Radar cross section Shape preserving design Topology optimization

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Influence of post-heat treatment on the microstructure and mechanical properties of Al-Cu-Mg-Zr alloy manufactured by selective laser melting

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Journal of Materials Science & Technology 2022年第16期111卷 35-48页

作者： Yanfang Wang Xin Lin Nan Kang Zihong Wang Yuxi Liu Weidong Huang State Key laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Key laboratory of metal High Performance additive manufacturing and innovative design MIIT ChinaNorthwestern Polytechnical UniversityXi’an 710072China

The properties of modified conventional wrought aluminum alloys cannot be significantly enhanced by normal post-heat treatment in that the fine-grained strengthening,arising from high cooling rate in SLM,is underutilized.In this work,compared with the normal T6 heat treatment,a novel simple direct aging regime was proposed to maintain the grain-boundary strengthening and to utilize the precipitation strengthening of secondary AlZr.It was found that a heterogeneous grain structure,which consisted of ultrafine equiaxed(~0.82μm)and columnar(~1.80μm)grains at the bottom and top of molten pool,respectively,was formed in the SLM processed sample.After direct aging(DA),the ultrafine grains were maintained and a mass of spherical coherent L1-AlZr particles with a mean radius of approximately1.15 nm was precipitated.In contrast,after solution treatment and aging(STA),a significant grain coarsening occurred in the equiaxed grain region.Meanwhile,the coarsening L1-AlZr particles,nano-sized S phases and GPB zones were detected in the STA sample.This subsequently induced that the yield strength of the DA sample(~435 MPa)was higher than that of the STA sample(~402 MPa)owing to the grain boundary strengthening and precipitation strengthening.Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys;this was comparable to that of the wrought AA2024-T6 alloy(~393 MPa).Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys;this was comparable to that of the wrought AA2024-T6alloy(~393 MPa).

关键词： Selective laser melting Al-Cu-Mg alloy Heat treatment Microstructure Mechanical properties

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Laser powder bed fusion of Zr-modified Al-Cu-Mg alloy:Processability and elevated-temperature mechanical properties

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Journal of Materials Science & Technology 2023年第5期136卷 223-235页

作者： Yanfang Wang Xin Lin Yufan Zhao Zihong Wang Xiaobin Yu Xuehao Gao Weidong Huang State Key laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Key laboratory of metal High Performance additive manufacturing and innovative design MIIT ChinaNorthwestern Polytechnical UniversityXi’an 710072China

Zr modification is an effective method for improving hot-cracking resistance and elevated-temperature mechanical properties during laser powder bed fusion(L-PBF)of traditional medium and high strength wrought aluminum alloys.This study investigated the l-PBF processability and elevated-temperature mechanical properties of a Zr-modified 2024Al alloy.It was found that the hot-cracking susceptibility increased with the increased scanning speed,which was in reasonable agreement with the modified Rappaz-Drezet-Gremaud criterion.Furthermore,the primary L1_(2)-Al_(3)Zr precipitates,which acted as ef-ficient nucleation sites,precipitated at the fusion boundary of the melt pool,leading to the formation of a heterogeneous grain structure.The yield strength(YS)of the as-fabricated samples at 150,250,and 350℃was 363,210,and 48 MPa,respectively.Despite the slight decrease to 360 MPa of the YS when tested at 150℃,owing to the additional precipitate strengthening from the L1_(2)-Al_(3)Zr precipitates,the YS achieved yield strengths of 253 and 69 MPa,an increase of 20.5%and 30.4%,when tested at 250 and 350℃,respectively.The yield strengths in both the as-fabricated and T6-treated conditions tested at 150 and 250℃were comparable to those of casting Al-Cu-Mg-Ag alloys and superior to those of traditionally heat-resistant 2219-T6 and 2618-T6 of Al-Cu alloys.

关键词： Laser powder bed fusion Zirconium Al-Cu-Mg alloy Processability Elevated-temperature mechanical property

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Microstructure and room-temperature tensile property of Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C with near equiaxed β grain fabricated by laser directed energy deposition technique

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Journal of Materials Science & Technology 2022年第6期101卷 308-320页

作者： MengCheng Deng Shang Sui Bo Yao Liang Ma Xin Lin Jing Chen State Key laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Key laboratory of metal High Performance additive manufacturing and innovative design MIIT ChinaNorthwestern Polytechnical UniversityXi’an 710072China

Near-equiaxed β grain was achieved in the near-α Ti60(Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C) titanium alloy via laser directed energy deposition(LDED). The microstructural evolution along the building direction and the room-temperature tensile properties along the horizontal and vertical directions(building direction) were systematically studied through SEM and OM. EBSD and XRD were utilized to accurately demonstrate the texture of the α and β phases. The results showed that the α phase presented a low texture intensity, which was ascribed to the weak textured β grain with near-equiaxed morphology, since there are Burgers orientation relationships during the β →α transition. In addition, numerical simulation, combined with the CET curve of Ti60 alloy considering the effect of multi-composition,was utilized to elucidate the formation mechanism of the near-equiaxed β grains. Furthermore, according to the solidification theory, we proposed that the solidification temperature range ΔTfwas more accurate than the growth restriction factor Q in predicting the formation tendency of equiaxed β grain in different titanium alloys. Tensile results showed that the horizontal and vertical samples had similar strength,while the former exhibited larger elongation than the latter. The effect of the near-equiaxed β grain and the internal α phase on mechanical properties were revealed at last.

关键词： Laser directed energy deposition Near-αtitanium alloy Equiaxedβgrain Room-temperature tensile property

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Interfacial Characteristics and Mechanical Behavior of Hybrid Manufactured AlSi10Mg–Al6061 Bimetal via Selective Laser Melting and Forging

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Acta metallurgica Sinica(English Letters) 2022年第3期35卷 375-388页

作者： Haoxiang Wang Xin Lin Nan Kang Zehao Qin Shuoqing Shi Jiacong Li Weidong Huang State Key laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072.China Key laboratory of metal High Performance additive manufacturing and innovative design MIIT ChinaNorthwestern Polytechnical UniversityXi'an 710072China

Hybrid manufacturing(HM)uses additive manufacturing(AM)techniques to prepare complex or fine structures on traditional processing parts,which can fully utilize the advantages of AM to form complex parts,and the high efficiency and low cost of conventional processing methods in manufacturing regular components.A bimetal material was produced by selective laser melting(SLM)of AlSi10Mg on the deformed Al6061 alloy substrate in this study.Firstly,the interface characteristics of the two alloys were studied.The results show that a metallurgical interface with a thickness of 100–200μm was formed as the result of the Marangoni convection during SLM preparation.In detail,the circular flow in the melt pool at the interface led to the dilution of alloying elements and the change of microstructure.Moreover,a suitable first-layer thickness can eff ectively suppress the hot cracks at the interfacial region.Based on the optimized results,the hybrid manufactured samples with diff erent SLM processed volume ratios(SLM-part)to the substrate were prepared to study the mechanical properties and the deformation behavior of hybrid parts.The results show that the volume ratio of the SLM-part to the substrate had an influence on the strength and the elasto-plastic behavior by aff ecting the distribution of plastic deformation.

关键词： Hybrid manufacturing Selective laser melting Forging Aluminum alloys Interface Mechanical behavior

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Collaborative optimization design of process parameter and structural topology for laser additive manufacturing

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Chinese Journal of Aeronautics 2023年第1期36卷 456-467页

作者： Shaoying LI Hongkai WEI Shangqin YUAN Jihong ZHU Jiang LI Weihong ZHANG State IJR Center of Aerospace design and additive manufacturing Northwestern Polytechnical UniversityXi’an 710072China miit Lab of metal additive manufacturing and innovative design Northwestern Polytechnical UniversityXi’an 710072China Unmanned System Research Institute Northwestern Polytechnical UniversityXi’an 710072China

High-resolution laser additive manufacturing(LAM)significantly releases design free-dom,promoting the development of topology optimization(TO)and advancing structural design methods.In order to fully take advantage of voxelated forming methods and establish the quantitative relationship between the mechanical properties of printing components and multiple process factors(laser-and process-parameters),the concurrent optimization design method based on LAM should cover the process-performance relationship.This study proposes a novel artificial intelligence-facilitated TO method for LAM to concurrently design microscale material property and macroscale structural topology of 3D components by adopting heuristic and gradient-based algorithms.The process–structure–property relationship of selective laser sintering is established by the back propagation neural network,and it is integrated into the TO algorithm for providing a systematic design scheme of structural topology and process parameter.Compared with the classical optimization method,numerical examples show that this method is able to improve the mechanical performance of the macrostructure significantly.In addition,the collaborative design method is able to be widely applied for complex functional part design and optimization,as well as case studies on artificial intelligence-facilitated product evaluation.

关键词： Back propagation neural network Gradient algorithm Laser additive manufactur-ing Process–structure–property Topology optimization

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High-performance liquid metal electromagnetic actuator fabricated by femtosecond laser

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International Journal of Extreme manufacturing 2024年第2期6卷 511-521页

作者： Yiyu Chen Hao Wu Rui Li Shaojun Jiang Shuneng Zhou Zehang Cui Yuan Tao Xinyuan Zheng Qianqian Zhang Jiawen Li Guoqiang Li Dong Wu Jiaru Chu Yanlei Hu CAS Key laboratory of Mechanical Behavior and design of Materials Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education InstitutesDepartment of Precision Machinery and Precision InstrumentationUniversity of Science and Technology of ChinaHefei 230027People’s Republic of China Key laboratory of Testing Technology for manufacturing Process of Ministry of Education Southwest University of Science and TechnologyMianyang 621010People’s Republic of China Department of Mechanical Engineering The University of Hong KongHong Kong Special Administrative Region of ChinaPeople’s Republic of China

Small-scale electromagnetic soft actuators are characterized by a fast response and simplecontrol,holding prospects in the field of soft and miniaturized robotics.The use of liquid metal(LM)to replace a rigid conductor inside soft actuators can reduce the rigidity and enhance the actuation performance and robustness.Despite research efforts,challenges persist in the flexible fabrication of LM soft actuators and in the improvement of actuation performance.To address these challenges,we developed a fast and robust electromagnetic soft microplate actuator based on a laser-induced selective adhesion transfer method.Equipped with unprecedentedly thin LM circuit and customized low Young’s modulus silicone rubber(1.03 kPa),our actuator exhibits an excellent deformation angle(265.25?)and actuation bending angular velocity(284.66 rad·s^(-1)).Furthermore,multiple actuators have been combined to build an artificial gripper with a wide range of functionalities.Our actuator presents new possibilities for designing small-scaleartificial machines and supports advancements in ultrafast soft and miniaturized robotics.

关键词： soft actuators femtosecond laser liquid metal

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Effect of dimensionless heat input during laser solid forming of high-strength steel

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Journal of Materials Science & Technology 2022年第4期99卷 127-137页

作者： Chunping Huang Renyu Liang Fenggang Liu Haiou Yang Xin Lin National Defense Key Discipline laboratory of Light Alloy Processing Science and Technology Nanchang Hangkong UniversityNanchang 330063China Key laboratory of metal High Performance additive manufacturing and innovative design MIIT ChinaNorthwestern Polytechnical UniversityXi’an 710072China

Laser solid forming(LSF)technology can be used to rapidly manufacture and repair high-strength steel parts with superior performance,but the value of the heat input during operation is difficult to quantify,which has a substantial impact on the microstructure and mechanical properties of the parts.A promising method to improve the forming efficiency and quality of LSFed parts is to accurately control the heat input and explore its relationship with the microstructure and mechanical properties.To remove the interference of other variables from the experiment,the dimensionless heat input Q;^(∗)was introduced.The Q^(∗)values were designed in advance to calculate the experimental parameters used to perform the LSF experiment.The microstructure was observed at different regions of the sample,and its mechanical properties were analyzed.From the results,the following conclusions were drawn.The Q;^(∗)value was directly related to the cooling rate and heat accumulation in the top structure,leading to the formation of different microstructures;it also modified the original structure at the bottom,affecting the subsequent thermal cycle and indirectly changing the tempered martensite morphology.The heat input also affected the mechanical properties of the sample.The hardness of the stable zone decreased with increasing Q;^(∗)value,and the lowest value was 190 HV.Similarly,the tensile strength and yield strength of the LSFed samples decreased considerably with increasing Q;^(∗)value,and the lowest values were 735 and 604 MPa,respectively.Only the elongation and reduction in the area increased after a slight decrease.The Q;^(∗)value had a significant effect on heat treatment.When Q;^(∗)=2.9,the increase in tensile strength and yield strength after heat treatment was the largest(29%and 44%,respectively).

关键词： Dimensionless heat input Laser solid forming High-strength steel Microstructure Mechanical property

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