Yoshinari Ishii

Anisotropic Nd/sub 2/Fe/sub 14/B based magnet powders with high remanences produced by modified HDDR process

The hydrogenation-decomposition-desorption-recombination (HDDR) process is a unique method to produce anisotropic Nd/sub 2/Fe/sub 14/B-based magnet powder for bonded magnet application. In this study, we studied the effect of appending the 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 treatment 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/sub 12.6/Fe/sub bal./Co/sub 17.4/B/sub 6.5/Zr/sub 0.1/Ga/sub 0.3/ powder are as follows: B/sub r/=1.06 T, H/sub cJ/=992 kA/m, and (BH)/sub max/=193 kJ/m/sup 3/. It was observed that the IA treatment induces rapid growth of a /spl 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 orientation of the final magnet powder.