Optimizing microstructure, magnetic properties and mechanical properties of sintered NdFeB magnet by double alloy method and grain boundary diffusion

This paper presents improvements in the coercivity, mechanical strength, and corrosion resistance of NdFeB magnets by modifying their microstructure using the double alloy method and grain boundary diffusion. The coercivity of magnet increases significantly from 16.66 kOe to 23.78 kOe with 0.64 wt% Tb usage. The overall magnetic performance (OMP) (BH)max (MGOe) + Hcj (kOe) of diffusion magnet improves approximately 7.09%. Furthermore, the mechanical properties and corrosion resistance are enhanced through the diffusion process. The microstructure forms thin intergranular phases of RE-Fe-O and a double core-shell structure consisting of Dy and Tb. These modifications contributed to the improved properties of NdFeB magnets. The formation mechanism of double core-shell is analyzed in detail. This work proposes a viable method for preparing high comprehensive performance magnet with a low Dy/Tb content.