Anisotropic Nd2Fe14B-based magnet powder with high remanence produced by modified HDDR process

The hydrogenation-decomposition-desorption-recombination (HDDR) process is a uniqe method to produce anisotropic Nd2Fe14B-based magnet powder for bond ed magnet application. In this study, we studied the effect of appending th e intermediate Ar (IA) treatment, i.e., hydrogenated materials are annealed under an Ar atmosphere before the evacuation treatment in the HDDR process , on the magnetic properties of magnet powder. It was found that the IA tre atment is very effective to enhance magnetic anisotropy of the powder. The optimum magnetic properties of the anisotropic bonded magnet made from the IA treatment processed Nd-12.6 Fe-bal.Co17.4B6.5Zr0.1Ga0.3 powder are as fo llows: B-r=1.06 T, H-cJ=992 kA/m, and (BH)(max)=193 kJ/m(3). It was observe d that the IA treatment induces rapid growth of alpha-(Fe,Co) grains in the decomposed mixture of the alloy. This microstructural change of the alloy is considered to be strongly related to the preferred crystallographic orie ntation of the final magnet powder.