Coercivity enhancement in HDDR near-stoichiometric ternary Nd-Fe-B powders

Anisotropic HDDR near-stoichiometric ternary Nd-Fe-B powders have been prepared. The coercivity of the powders was improved from 208.6 to 980.1 kA/m by the subsequent diffusion treatment using the Pr-Cu alloy. For comparison, Nd11.5Fe80.7B6.1Pr1.2Cu0.5 alloy, in which Pr and Cu elements were directly added into the original Nd-Fe-B alloy, was also treated by the same HDDR process and the coercivity was only 557.3 kA/m. Microstructural investigations showed that a large area of (Nd, Pr)-rich phases concentrated at triangle regions in the HDDR Nd11.5Fe80.7B6.1Pr1.2Cu0.5 powders, while the (Nd, Pr)-rich phases distributed uniformly in the diffusion treated powders. The uniform grain boundary layer can pin the motion of domain wall more effectively, resulting in a higher coercivity in diffusion treated HDDR Nd-Fe-B powders.