Kazunori Igarashi

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.

Influences of original alloy microstructure on magnetic properties of isotropic HDDR-treated Nd–Fe–B powder

Abstract Influences of original alloy microstructure on magnetic properties of the isotropic hydrogenation-decomposition-desorption-recombination-treated Nd 12.6 Fe 79.0 Co 2.4 B 6.0 powder were studied using two types of starting materials, i.e., the strip cast (SC) alloy and the conventional book-mold cast (BMC) alloy. It was found that the powder prepared from the SC alloy exhibits better I – H loop squareness and higher remanence than the powder from the BMC alloy. The powder obtained from the SC alloy consists of the recombined Nd 2 Fe 14 B grains with more uniform size, which is thought to be closely related to its good loop squareness. The effect of using the SC alloy could be attributed to the complete elimination of α-Fe phase.