Effect on Microstructure and Magnetic Properties of Nd-Fe-B Magnets Through Grain Boundary Diffusion of Tb and Multi-Component Alloys

In this study, commercial Nd-Fe-B magnets were utilized as starting materials to investigate the impact of various Tb-containing diffusion sources on the magnetic properties. Tb, Tb60Nd5Al30Ga5, and Tb65Pr10Nd5Al5Cu10Ga5 were developed as diffusion sources. After grain boundary diffusion treatment, the magnetic parameters of the magnets were evaluated at 20 °C, 90 °C, and 140 °C. The composition, microstructure, and elemental distributions of the magnets before and after diffusion were examined. It was found that the inherent coercivity of the magnets showed a dramatic increment of 49.4% at 20 °C after diffusion with Tb-containing alloys. The benefits and drawbacks of the designed diffusion sources were thoroughly discussed. Magnets diffused with the Tb65Pr10Nd5Al5Cu10Ga5 source displayed the highest overall performance, generating a thin layer with a grid-like structure at the grain boundaries and a consistent shell structure of Tb around the main phase grains. This work offers a promising alternative in the optimization of Nd-Fe-B magnets.