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摘要
The desorption-recombination behavior of a mechanically disproportionated, nanostructured Nd12Fe82B6 alloy was investigated by differential scanning calorimetry and thermogravimetric analysis. The microstructure change due to desorption-recombination treatments at various temperatures was characterized by x-ray diffraction, Mossbauer study, and transmission electron microscopy observation. The results show that the hydrogen desorption of the as-disproportionated alloy occurs in two stages: (i) the partial dehydriding of the Nd hydride from Nd2H5 to NdH2, as well as the desorption of the hydrogen absorbed/adsorbed at sites of crystal defects but not in the form of Nd hydride, at temperatures between 180 and 460 C; and (ii) the complete dehydriding of the Nd hydride from NdH2 to Nd at temperatures between 630 and 780 C. The recombination of alpha-Fe with Fe2B and Nd to form Nd2Fe14B occurs following the dehydriding of NdH2 to Nd, and it acts as the controlling step for the whole desorption-recombination process. The kinetics of both the desorption-recombination reaction and the growth of the newly formed Nd2Fe14B grains accelerate with increasing temperature. For a fixed annealing time of 30 min, the optimal processing temperature seems to be 760 C, which gives rise to a fully recombined Nd2Fe14B-alpha-Fe nanocomposite microstructure with Nd2Fe14B and alpha-Fe phases of 25-30 nm in average size.
- 出版日期2008-2
- 单位哈尔滨工业大学
