  Laser powder bed fusion is a well-established additive manufacturing method
that can be used for the production of net-shaped Nd-Fe-B sintered magnets.
However, low coercivity has been one of the drawbacks in the laser powder bed
fusion processed Nd-Fe-B magnets. In this work, we have demonstrated that the
grain boundary diffusion process using low-melting Nd-Cu, Nd-Al-Ni-Cu, and
Nd-Tb-Cu alloys to the selective laser sintered NdFeB magnets can results in a
substantial enhancement of coercivity from 0.65 T to 1.5 T. Detailed
microstructure investigations clarified formation of Nd-rich grain boundary
phase, introducing Tb-rich shell at the surface of Nd2Fe14B grains, and
maintaining the grain size in nano-scale are responsible for the large
coercivity enhancement.
