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Extraordinary simultaneous enhancement of the coercivity and remanence of dual alloy HRE-free nd-fe-b sintered magnets by post-sinter annealing

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Journal of Materials Science & Technology 2022年第11期106卷 236-242页

作者： Qingfang Huang Qingzheng Jiang Jifan Hu Sajjad Ur Rehman Gang Fu Qichen Quan Jixiang Huang Deqin Xu Dakun Chen Zhenchen Zhong Jiangxi Key Laboratory for Rare Earth Magnetic Materials and Devices&College of Rare Earths Jiangxi University of Science and TechnologyGanzhou 341000China Fujian Key Laboratory for Rare Earth Functional Materials Longyan 366300China School of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China

Post-sinter annealing process plays an important role in the microstructures and magnetic properties of the nd-fe-b sintered *** this paper,systematically investigated are the magnetic properties and microstructures of the as-sintered and post-sinter annealed nd-fe-b magnets with Pr-fe-Ga boundary *** choice consecutive annealing methods are adopted at high and low temperatures,namely the 1 st annealing at 880℃ for 2 h and then the 2^(nd) annealing at 440℃ for 3 *** is exceptional to find out that both the remanence and coercivity are improved after 2^(nd) annealing process for this type of *** coercivity is hugely increased from 10.09 kOe for the as-sintered sample to 17.19 kOe for the 2^(nd) annealed magnet,with a significant increment of 70.37%in *** extraordinary magnetic properties of b_(r)=14.44 kGs,H_(cj)=17.19 kOe and(bH)_(max)=51.08 MGOe are obtained for the designated nd-fe-b sintered magnets without heavy rare earth(HRE)elements manufactured by dual alloy *** Curie temperature is monotonically decreased from 634 K to 602 K while the c-axis alignment degree is optimized after *** observation and analysis indicate that the elemental distribution patterns are altered after the 2^(nd) *** diffusion of the aggregate(Pr,nd,Cu,Ga)-rich phase from triple junctions into the grain boundary regions is ascribed to the formation of thin and continuous grain boundary layer,which is critical to improve the microstructures and magnetic properties.

关键词： nd-fe-b sintered magnets HRE-free Dual alloy method Post-sinter annealing Magnetic properties

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Improvement in magnetic properties,corrosion resistance and microstructure of nd-fe-b sintered magnets through intergranular addition of Tb_(68)Ni_(32)

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Journal of Rare Earths 2022年第5期40卷 784-791,I0004页

作者： Jia Li Qingrong Yao Weichao Huang Jue Xie Zhilin Mo Jianqiu Deng Jiang Wang Guanghui Rao Huaiying Zhou Guangxi Key Laboratory of Information Materials School of Materials Science and EngineeringGuilin University of Electronic TechnologyGuilin 541004China China Rare Metals and Rare Earth(Guangxi)Jinyuan New Materials Co. Ltd.Hezhou 542603China

New energy vehicles and offshore wind power industries have a high demand for sintered nd-fe-b magnets with high intrinsic coercivity and high corrosion *** this study,the magnetic properties,anticorrosion properties,and micro structure of nd-fe-b sintered magnets with the intergranular addition of low-melting-point eutectic Tb_(68)Ni_(32) alloy powders were *** aim is to determine if the addition of Tb_(68)Ni_(32) can improve these properties.A low melting-point eutectic alloy Tb_(68)Ni_(32) powders was prepared as a grain boundary additive and blended with the master alloy powders prior to *** coercivity of the resultant magnets gradually increases from 1468 to 2151 kA/m by adding increasing amounts of Tb_(68)Ni_(32).At the same time,the remanence first increases and then slightly *** studying the microstructure and elemental composition of the Tb_(68)Ni_(32) added magnets,it is found that the significant increase in coercivity and the negligible reduction in remanence is due to densificatio n,improved grain orientation,a unifo rm and continuous boundary phase distribution,as well as the generation of a(nd,Pr,Tb)_(2) fe_(14)b "core-shell" structure surrounding the main-phase ***,the corrosion resistance of the magnet is greatly improved owing to the enhancement of electrochemical stability,as well as the optimization of the distribution and morphology of the intergranular phase.

关键词： nd-fe-b sintered magnets Tb_(68)Ni_(32)alloy Magnetic properties Corrosion resistance Microstructure Rare earths

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Effect of yttrium substitution on magnetic properties and service performances of nd-fe-b sintered magnets

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Journal of Rare Earths 2023年第1期41卷 116-121页

作者： Xiaodong Fan Shuai Guo Guangfei Ding Sining Fan Zhehuan Jin Renjie Chen Shukai Zhang Aru Yan CAS Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo 315201China Chinalco Shandong Yinuowei Strong Magnetic Material Co. LtdTaian 271600China

We successfully fabricated partial Y substituted ndY-fe-b magnets with nominal compositions of(nd_(1-x)Y_(x))_(13.80)fe_(ba1)Al_(0.24)Cu_(0.1)b_(6.04)(at%,x=0,0.1,0.2,0.3,0.4) by powder metallurgy process and the magnetic properties as well as service performances of the magnets were also systematically *** phase constituents of the magnets have no obvious variation within the whole range of Y content,while the main phase grains form in-situ core-shell structure where Y gathers in the core and nd mainly distributes in the *** with pure nd-fe-b magnets,the magnetic performances of Y substituted magnets slightly decrease on account of the poor intrinsic magnetic properties of Y_(2)fe_(14)***,the μ_(O)M_(r),μ_(O)H_(cj) and(bH)_(max) of the 20 at% Y magnet still remain at a high level of 1.325 kG,1.173 kOe and 342.884 kj/m^(3),which approaches the performances of commercial N45-grade *** service performances of Y substituted magnets indicate that though the surface corrosion products and Vickers hardness of the ndY-fe-b magnets increase to a certain extent compared to nd-fe-b,the magnets with Y substitution still display relatively good service ***,on the basis of sacrificing little partial magnetic and service performances,Y substituted nd can still prepare ndY-fe-b medium-grade *** this way,we achieve the balanced utilization of rare earth resources,which has significant meanings for the industry and scientific research.

关键词： Y substitution Magnetic properties Service performances nd-fe-b sintered magnets Rare earths

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Coercivity enhancement mechanism of Tb-diffusion nd-fe-b sintered magnets studied by magneto-optical Kerr optical microscope

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Rare Metals 2021年第3期40卷 570-574页

作者： Dan Wu Wei-Qiang Liu Ming Yue Qiong Wu Dong-Tao Zhang Qing-Mei Lu Xu-Liang Li Jing-Wu Chen Key Laboratory of Advanced Functional Materials College of Materials Science and EngineeringBeijing University of TechnologyMinistry of Education of ChinaBeijing 100124China State Key Laboratory of Rare Earth Permanent Magnetic Materials Hefei 231500China

The coercivity,microstructure,and magnetic domain structure of nd-fe-b sintered magnets by grain boundary diffusion process(GbDP) with TbH3 nanoparticles were systematically *** to the original magnet,the coercivity(Hci) of the GbDP magnets improved from 1702 to 2374 kA·m^(-1) with few remanence reduced from 1.338 to 1.281 *** probe microanalysis(EPMA) analysis showed that Tb diffused along grain boundary,mainly concentrated in the boundary layer of the main phase,and formed a core-shell ***-optical Kerr optical microscope(MOKE) analysis showed that there were two types of magnetic domain reversal in one grain:gradual reversal(GR) and abrupt reversal(AR).When the applied field decreased from saturated magnetic field,the reversal magnetic domain nucleated and then spread over the whole grain gradually,which was called ***,some grains kept the single domain state until Hh which was a value of reverse direction applied field in second quadrant in hysteresis *** the applied field increased above Hh,reversed magnetic domain would suddenly appear and occupy most of the area of the grain,which was called *** is because AR grains have higher reversed magnetic domain nucleation field(HRN2) than GR grains(HRN1).After GbDP,the area of AR region increased obviously and GR region decreased accordingly,indicating that the core-shell structure could change GR grain into AR *** coreshell structure could suppress flipping of the magnetization of the grains due to the large magnetic anisotropy of Tbrich ***,large AR area led to high coercivity.

关键词： Coercivity enhancement mechanism Magnetic domain Grain boundary diffusion nd-fe-b sintered magnets

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Electrochemical Corrosion behavior of nd-fe-b sintered magnets in Different Acid Solutions

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Journal of Rare Earths 2006年第2期24卷 218-222页

作者：郑精武姜力强陈巧玲 Department of Chemical and Materials Engineering Zhejiang University of Technology Hangzhou 310014 China Department

Electrochemical corrosion behavior of nd-fe-b sintered magnets in nitric acid, hydrochloric acid, sulfuric acid, phosphate acid and in oxalic acid was studied. Potentiodynamic polarization curves and immersion time dependence of corrosion rates of nd-fe-b sintered magnets in different acid solutions were tested. Microstructures of corroded nd-fe-b sintered magnets were investigated by means of SEM and AFM. The results indicate that in strong acid solutions of similar hydrogen ion concentration, the corrosion current increases in the order of HCl 〉 H3SO4 〉 HNO3 solution and nd-fe-b sintered magnets are passivated in phosphate acid and oxalic acid. Within 25 min, the corrosion rates of nd-fe-b sintered magnets in H2SO4 and H3PO4 solutions show a declining trend with immersion time, while in HNO3 and HCl solutions the corrosion rates are rising. And in H2C2O4 solution, weight of the magnets increases. The brim of nd-fe-b sintered magnets is corroded rather seriously and the size of the magnets changed greatly in nitric acid. The surfaces of the corroded magnets in the above mentioned acid solutions are all coarse.

关键词： nd-fe-b sintered magnets corrosion acid solution microstructure rare earths

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Influencing Factors on Corrosion Resistance of nd-fe-b sintered magnets Coating

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Journal of Rare Earths 2006年第S2期 207-210页

作者：郑精武游李顺乔梁姜力强 College of Chemical Engineering and Materials Science Zhejiang University of Technology College of Chemical Engineering and Materials Science Zhejiang University of Technology Hangzhou 310032 China

Factors that affect corrosion resistance of the protective coatings over nd-fe-b sintered magnets, such as microstructure of nd-fe-b sintered substrate, acid solutions for cleaning oxide on the magnets surfaces, etc. were investigated. Microstructure of the substrate was observed through AFM, its corrosion model was made, the bonding between the magnets and the coatings was investigated with SEM, and corrosion characteristics of nd-fe-b sintered substrate in some general acid solutions and in NaCl solution after coating were measured respectively through potentioynamic polarization technique. The results show that nd-fe-b sintered substrate has porous structure, and multi-coating is a relatively effective way to seal the pores; the oxide is eliminated more efficiently in nitric acid and vitriol, and the bonding between the magnets and the coatings is comparatively strong when the matrix is washed in vitriol; with the same thickness, corrosion resistance of the nickel-plate by electrodeposited with direct current power is stronger than by plated in other ways. by analyzing the instant model of the electroplate roller, we find that the sample was chemically eroded during the rolling process.

关键词： nd-fe-b sintered magnets coating corrosion resistance

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高性能钕铁硼磁体的晶界调控与性能增强机制研究（英文）

高性能钕铁硼磁体的晶界调控与性能增强机制研究（英文）

引用

中国稀土学会2021学术年会

作者：黄清芳江庆政 Sajjad Ur Rehman 钟震晨江西理工大学福建省稀土功能材料重点实验室

Post-sinter annealing process plays an important role in the microstructures and magnetic properties of the nd-fe-b sintered *** this paper,systematically investigated are the magnetic properties and microstructures of the as-sintered and post-sinter annealed nd-fe-b magnets with Pr-fe-Ga boundary *** choice consecutive annealing methods are adopted at high and low temperatures,namely the1 annealing at 880oC for 2 h and the 2 annealing at 880oC for 2 h and then 440oC for 3 *** is exceptional to find out that both the remanence and coercivity are improved after 2 annealing process for this type of *** coercivity is hugely increased from 10.09 kOe for the as-sintered sample to 17.19 kOe for the 2 annealed magnet,with a significant increment of 70.37%in *** extraordinary magnetic properties of br=14.44 kGs,Hcj=17.19 kOe and (bH)max=51.08 MGOe are obtained for the designated nd-fe-b sintered magnets without heavy rare earth (HRE)elements manufactured by dual alloy *** Curie temperature is monotonically decreased from 634 K to 602 K while the c-axis alignment degree is optimized after *** observation and analysis indicate that the elemental distribution patterns are altered after the 2 *** diffusion of the aggregate(Pr,nd,Cu,Ga)-rich phase from triple junctions into the grain boundary regions is ascribed to the formation of thin and continuous grain boundary layer,which is critical to improve the microstructures and magnetic properties.

关键词： nd-fe-b sintered magnets HRE-free Dual alloy method Post-sinter annealing Magnetic properties

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