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.