Crystallization process of α-Fe/Nd2Fe14B type nanocomposite magnet alloys

The crystallization process of alpha-Fe/Nd2Fe14B type nanocomposite magnet alloys has been studied with the x-ray diffraction method and Mossbauer spectroscopy. Melt-spun alloy ribbons with the compositions of Nd8Fe81Co4Nb0.5B6.5 and Nd9Fe79Co4Nb1.B-5(6.5) were annealed at 600, 650, 700 and 750 degreesC for the former, and at 700 degreesC for the latter, respectively. In the case of Nd8Fe81Co4Nb0.5B6.5, the alpha-Fe and Nd2Fe14B phases appear in the very early stage of the crystallization process, that is at 650 degreesC. On the other hand, the alloy of Nd9Fe79Co4Nb1.5B6.5 annealed at 700 degreesC has fewer alpha-Fe and more Fe3B phases compared with the case of Nd8Fe81Co4Nb0.5B6.5. Discussions taking notice of the atomic ratio of Fe in the above alloys lead us to the conclusion that alpha-Fe and Nd2Fe14B are crystallized at comparatively low annealing temperature when the Fe ratio is high in the alloys, while fewer alpha-Fe and more Fe3B phases appear when the Fe ratio is low.