Formation of anti-shell/core structure of heavy rare earth elements (Tb, Dy) in sintered Nd-Fe-B magnet after grain boundary diffusion process

• DOI: 10.1016/j.scriptamat.2018.12.034
• Publication Date: 2019-01-09T16:48:52Z
• Authors: Weidong Li; Qingke Zhang; Qihang Zhu; Song Xiao; Cheng Xu; Lijing Yang; Bizhang Zheng; Shoudong Mao; Zhenlun Song
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract The evolution of microstructure close to the surface of sintered Nd-Fe-B magnet after grain boundary diffusion process (GBDP) of heavy rare earth elements (HREE, Tb, Dy) was investigated. It was found that two new types of microstructure, anti-shell/core and no-shell structures, were formed in the magnet with the diffusion time longer than 0.5 h. The anti-shell/core structure was formed due to an abnormal diffusion of HREE from grain to grain boundary based on the dual-trend diffusion model, it contributes a negative effect on the coercivity of diffused magnets.