Utility and influence mechanism of densification modulation on grain boundary diffusion in NdFeB magnets  

作　　者：San'gen Luo Munan Yang Shuwei Zhong Sajjad Ur Rehman Jiajie Li Xiaoqiang Yu Bin Yang 

机构地区：[1]College of Rare Earths,Jiangxi University of Science and Technology,Ganzhou,341000,China [2]National Rare Earth Functional Material Innovation Center&Guorui Scientific Innovation Rare Earth Functional Materials Co.,Ltd.,Ganzhou,341000,China

出　　处：《Journal of Rare Earths》2025年第3期569-577,I0006,共10页稀土学报(英文版)

基　　金：Project supported by the National Natural Science Foundation of China(52361033);National Key Research and Development Program(2022YFB3505400);Ministry of Industry and Information Technology Heavy Rare Earth Special Use of Sintered NdFeB Project(TC220H06J);Academic and Technical Leaders in Major Disciplines in Jiangxi Province(2022BCJ23007);Jiangxi Province Science and Technology Cooperation Key Project(20212BDH80007);Jiangxi Graduate Student Innovation Special Fund Project(YC2023-B213)。

摘　　要：Grain boundary diffusion technology is pivotal in the preparation of high-performance NdFeB magnets.This study investigates the factors that affect the efficiency of grain boundary diffusion,starting from the properties of the diffusion matrix.Through the adjustment of the sintering process,we effectively prepared magnets with varied densities that serve as the matrix for grain boundary diffusion with TbH,diffusion.The mobility characteristics of the Nd-rich phase during the densification stage are leveraged to ensure a more extensive distribution of heavy rare earth elements within the magnets.According to the experimental results,the increase in coercivity of low-density magnets after diffusion is significantly greater than that of relatively high-density magnets.The coercivity values measured are 805.32 kA/m for low-density magnets and 470.3 kA/m for high-density magnets.Additionally,grain boundary diffusion notably enhances the density of initial low-density magnets,addressing the issue of low density during the sintering stage.Before the diffusion treatment,the Nd-rich phases primarily concentrate at the triangular grain boundaries,resulting in an increased number of cavity defects in the magnets.These cavity defects contain atoms in a higher energy state,making them more prone to transition.Consequently,the diffusion activation energy at the void defects is lower than the intracrystalline diffusion activation energy,accelerating atom diffusion.The presence of larger cavities also provides more space for atom migration,thereby promoting the diffusion process.After the diffusion treatment,the proportion of bulk Nd-rich phases significantly decreases,and they infiltrate between the grains to fill the cavity defects,forming continuous fine grain boundaries.Based on these observations,the study aims to explore how to utilize this information to develop an efficient technique for grain boundary diffusion.

关 键 词：NdFeB magnets DENSITY Grain boundary diffusion Defect utility Rare earths 

分 类 号：TM273[一般工业技术—材料科学与工程]