Coercivity enhancement of anisotropic Dy-free Nd–Fe–B powders by conventional HDDR process

Coercivity enhancement of Dy-free Nd–Fe–Co–B–Ga–Zr powders was studied using the conventional hydrogenation–decomposition–desorption–recombination (HDDR) process. It was found that the addition of Al together with the proper Nd content and the slow hydrogen desorption of the HDDR treatment can induce high coercivity in the powder. For example, the 14.0at% Nd–2.0at% Al powder exhibits HcJ of 1560kA/m, Br of 1.22T, and (BH)max of 257kJ/m3. The high coercivity inducement of the powder is thought to be attributed to the formation of Nd-rich phase, which continuously surrounds fine Nd2Fe14B grains. ► The Al addition enhances coercivity of HDDR-processed Dy-free Nd–Fe–B powders. ► This might be attributed to the formation of Nd-rich grain boundary (GB) phase. ► Larger Nd contents develop the GB phase and then improve the coercivity further.