Structural studies of some hydrogen-treated materials related to the HDDR-process of Nd/sub 2/Fe/sub 14/B-based alloys

Hydrogen-treated Nd/sub 14.0/Fe/sub 66.9/Co/sub 11.0/Ga/sub 1.0/Zr/sub 0.1/B/sub 7.0/ alloys have been examined by means of powder X-ray diffraction (XRD) and electron probe microanalysis (EPMA) to understand the mechanism of the development of magnetic anisotropy in the hydrogenation, decomposition, desorption, and recombination (HDDR) process of Nd/sub 2/Fe/sub 14/B-based alloys. It has been revealed that Nd/sub 2/Fe/sub 14/B phase can coexist in equilibrium with decomposed products, namely, /spl alpha/-Fe, NdH/sub 2/, and Fe/sub 2/B, in the presence of hydrogen of an atmospheric pressure over the temperature ranging 1113 to 1153 K. It was observed that Co and Ga condensed into a Nd/sub 2/Fe/sub 14/B phase during hydrogen-treatments, resulting in a thermodynamically stable Nd/sub 2/(Fe,Co,Ga)/sub 14/B compound. Well-developed anisotropic materials were obtained via the HDDR-process when the hydrogen-treatment was accomplished under such conditions that Nd/sub 2/(Fe,Co,Ga)/sub 14/B coexists with the decomposed products. All our results give a favorable support to the previous proposal that the crystallographic orientation of the original alloy can be conveyed via the undecomposed Nd/sub 2/Fe/sub 14/B particles through-out HDDR processing.