Achieving 2.8 T coercivity in Nd-Fe-B sintered magnets subjected to DyCu and PrCu grain boundary diffusion process

There has been a concern about the over-consumption of scarce and expensive heavy rare-earth elements (HREs), such as Dy and Tb, in achieving high coercivity in Nd-Fe-B magnets. This work reports an approach to achieve a high coercivity of 2.8 T by sequentially diffusing Dy
70
Cu
30
and Pr
68
Cu
32
eutectic alloys in fine-grained sintered magnets fabricated by a press-less process. The coercivity of 2.8 T was achieved for its low Dy content of only 0.9 wt.%. The Pr
68
Cu
32
diffusion facilitated the infiltration of Dy towards the center of the magnets, resulting in uniform Dy-rich shell formation in the whole sample. Such a unique shell structure increased the anisotropy field of the shell to realize the 2.8 T coercivity.