烧结Nd-Fe-B磁体表面渗镀Dy2O3对磁体显微组织和磁性能的影响

Effect of Dysprosium Addition by Pack Cementation on Magnetic Properties and Microstructure of Nd-Fe-B Sintered Magnets

研究了烧结Nd-Fe-B磁体表面渗镀Dy2O3对磁体组织结构与磁性能的影响。表面渗镀Dy2O3后,N40的矫顽力由1017 kA.m-1提高到1146 kA.m-1,38H的矫顽力由1575 kA.m-1提高到1753 kA.m-1,而通过传统合金化添加同量Dy,N40和38H的矫顽力分别为1061和1634 kA.m-1。磁体表面渗镀Dy2O3后热稳定性也大大改善。组织分析表明,元素Dy从表面扩散并渗入磁体的内部约20μm厚,Nd2Fe14B晶粒表层附近Dy含量比晶界中高,说明Dy2O3中的Dy通过扩散与富Nd相及Nd2Fe14B晶粒表面层的部分Nd发生置换反应,增强了Nd2Fe14B晶粒表面层的磁晶各向异性。在此基础上,提出了高矫顽力高热稳定性渗Dy的烧结Nd-Fe-B磁体中Dy分布的理想模型。

Effect of Dy addition by pack cementation on magnetic properties and microstructure of Nd-Fe-B sintered magnets was investigated. The intrinsic coercivity increased from 1017 kA.m^-1 to 1146 kA.m^-1 for N40 and from 1575 kA.m^-1 to 1753 kA.m^-1 for 38H by pack cementation. It was much higher than 1061 and 1634 kA.m^-1 for N40 and 38H, respectively, by conventional alloying the same Dy content. The thermal stability of the magnet was improved by pack cementing Dy. The microstructure analyses showed that Dy was rich in the depth of 20 μm from the surface. The Dy was the richest in the extension layer of NdEFeInB grains, indicating Dy in Dy2O3 powder diffused and substituted Nd was in Nd-rich phase and the extension layer of Nd2Fe14B grains, which increased magnetic anisotropy of the extension layer of NdEFe14B grains. Furthermore, ideal model of Dy distribution in Nd-Fe-B sintered magnets with high intrinsic coercivity by pack cementation was presented.