Hydrogenation-assisted crystallisation of amorphous Nd-Fe-B material

Crystallisation of the Nd-Fe-B amorphous material assisted by a hydrogenation was investigated. The Nd-Fe-B amorphous material was prepared by mechanical milling of the Nd15Fe77B88 alloy ingot. The amorphous material was reacted with hydrogen gas to cause crystallisation. The hydrogenation facilitated the crystallisation of the amorphous Nd15Fe77B8 alloy, and the crystallisation was completed at the temperatures much lower than the ordinary thermal crystallisation temperature. The huge heat evolved from the hydrogenation assisted the crystallisation of the amorphous. The Nd15Fe77B8 material crystallised from the amorphous by the hydrogenation consisted of a mixture of NdHx, Fe and Nd1+xFe4B4 phases. The desorption of hydrogen from the mixture under vacuum at an elevated temperature led to a combination of Nd, Fe and Nd1+xFe4B4 phases into the Nd2Fe14B phase. The hydrogenation-assisting crystallised material showed much higher coercivity after the desorption and combination with respect to the material thermally annealed without hydrogenation. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)