The hydrogenatlqn-decompösition-desorptlonrecombination (HDDR) process is a unlqe method to produce anisotropic Ni)2FeuB-hased magnet powder for bonded magnet application. In this study, we studied the effect of appending the intermediate Ar (IA) treatment, Le., 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 Nd12.6 FebalCo17.4B6.5Zr0Oa0.3 powder are as follows Br=1.06 T, Hcj=992 ItA/m, and (BH)max=193 kJ/m3.It was observed that the IA treatment induces rapid growth of a -(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.
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