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低熔点元素及合金改性HDDR钕铁硼磁粉的研究进展
吕蒙, 李文献, 朱明原, 胡业旻, 金红明, 李瑛
上海大学 材料科学与工程学院 微结构重点实验室, 上海 200072
摘要:
氢化-歧化-脱氢-再复合(HDDR)工艺是制备各向异性钕铁硼(NdFeB)磁粉的主要方法.但HDDR磁粉实际矫顽力(HC)较低,重稀土元素Dy的引入可以显著提高其HC,经研究发现引入的Dy主要分布于磁体晶界,起调控晶界相的作用:增加晶界厚度,提高磁粉的各向异性场(HA).但重稀土元素Dy自然资源匮乏且价格昂贵,限制了HDDR磁粉的发展.为减少磁粉中重稀土元素用量、降低成本,研究人员通过晶界扩散低熔点元素及合金来替代重稀土元素Dy,因低熔点物质在扩散过程中呈液相,提高了扩散介质与晶界相的接触面积及扩散系数,有利于其沿晶界扩散并调控晶界相,使磁粉HC提高.对近些年晶界扩散低熔点元素及合金提高HDDR-NdFeB磁粉HC的部分研究成果进行了归纳.
关键词:  HDDR磁粉  晶界扩散  矫顽力  低熔点金属  微观结构
DOI:10.3969/J.ISSN.1000-5137.2017.06.014
分类号:TM273
基金项目:国家自然科学基金委员会面上项目(51572166);上海高校特聘教授(东方学者)岗位计划项目(TP2014 041)
Progress of HDDR NdFeB powders modulated by the diffusion of low melting point elements and their alloys
Lyu Meng, Li Wenxian, Zhu Mingyuan, Hu Yemin, Jin Hongming, Li Ying
Laboratory for Microstructures, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China
Abstract:
The hydrogenation-disproportionation-desorption-recombination (HDDR) process is the main technique for the fabrication of anisotropic NdFeB magnetic powder.But the intrinsic coercivity (HC) of HDDR magnetic powder is low.The addition of heavy rare earth element Dy could improve its HC.It was found that the added Dy is mainly distributed in the grain boundary of HDDR magnets,which regulates grain boundary phase and increases the thickness of grain boundary to improve the anisotropy field (HA) and HC of the magnets.However,Dy becomes scarcer and more expensive,which limits the practical application of HDDR magnets.To reduce the dependence on heavy rare earth elements and cost,researchers replaced the heavy rare earth element Dy by low melting point elements and their alloys through grain boundary diffusion technique.During diffusion process low melting point metal exists as liquid phase that increases the diffusion coefficient of diffusion medium as well as its contact area with grain boundary phases of HDDR magnets,and benefits its diffusion along grain boundaries and regulation of grain boundary phase.The modified grain boundary in magnets improve HC.This review paper focuses on the research progress in improving HC of HDDR NdFeB magnets by low melting point elements and their alloys.
Key words:  HDDR power  grain boundary diffusion  coercivity  low melting metal  microstructure