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Abstract

A production method to produce an anisotropic NdFeB based alloy magnet having a high anisotropic ratio and coercivity by a simple procedure. The production method consists of a first hydrogenation process, a second hydrogenation process and a desorption process. The first hydrogenation process at a low temperature produces the hydride that stores hydrogen needed in advance of the phase transformation. After that, the second hydrogenation process at an elevated temperature proceeds smoothly at a moderate reaction rate of the phase transformation and produces the mixture of NdH.sub.2, Fe and Fe.sub.2 B from the hydride in addition to making the crystallographic orientation of Fe.sub.2 B phase consistent with the original R.sub.2 Fe.sub.14 B matrix phase. Subsequently, the desorption process produces the fine grained microstructure of Nd.sub.2 Fe.sub.14 BHx with high degrees of alignment of the crystallographic orientation consistent with the original crystallographic orientation of Fe.sub.2 B phase. Fine and uniform grained microstructure of RFeB based alloy is produced by recombination of the mixture during the hydrogen heat treatment and consequently offers the anisotropic rare earth magnet powder to have a high anisotropic ratio and high coercivity.

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