Highly efficient Tb-utilization in sintered Nd-Fe-B magnets by Al aided TbH2 grain boundary diffusion

Al aided TbH2 grain boundary diffusion (GBD) was applied to sintered Nd-Fe-B magnet in comparison with the TbH2 GBD magnet. The coercivity was enhanced from 13.73 kOe to 23.29 kOe, higher than the 22.26 kOe of TbH2 GBD magnet. The Tb content in the bulk magnet was reduced to 0.47 wt%, much lower than the 1.85 wt% of the TbH2 GBD magnet. Microstructure analysis showed that continuous grain boundary phases were formed and completely enveloped the grains with thin Tb-rich shells, which can be attributed to the reduced Tb content in diffusion source and the promoted GBD aided by Al. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved