A new strategy for improving the Tb utilization efficiency in sintered NdFeB magnets through pressure-assisted grain boundary diffusion

Improving the utilization efficiency of heavy rare earth is currently a research hotspot in the field of rare earth permanent magnets. In this article, the effect and mechanism of pressure-assisted grain boundary diffusion (PGBD) on improving Tb utilization efficiency was investigated. The magnetic properties, microstructure, and magnetic domain morphology of the PGBD magnets were compared and analyzed in relation to conventional grain boundary diffusion (CGBD) magnets. The results shows that the PGBD process promoted Tb diffusion into the magnets. The residual layer thickness of the PGBD magnets was thinner than that of the CGBD magnets, demonstrating that the PGBD process could allow more Tb to diffuse into the magnets. The formation of a more complete and deeper core-shell structure in the PGBD magnets significantly enhances their resistance to demagnetization fields, thereby resulting in an increased coercivity. The PGBD process exhibits a reduction in TbH3 usage by approximately 0.2 wt.% compared to the CGBD process, while maintaining an equivalent level of coercivity increment. These findings highlight the efficacy of the PGBD process in enhancing Tb utilization efficiency and conserving Tb resources.