Microstructural evolutions in NdFe10.5Mo1.5NX and Pr13Fe80B7 compounds during hydrogenation-disproportionation desorption recombination process

Microstructural changes of NdFe10.5Mo1.5 and Pr13Fe80B7 compounds during the solid-hydrogenation disproportionation desorption recombination process are investigated in this paper. It is found that the early disproportionated microstructure of NdFe10.5Mo1.5 and Pr13Fe80B7 alloys shows similar rodlike morphology. All the NdH2+X and PrH2+X rods have the same orientation and grow with a definite orientation related to the alpha-Fe matrix. However, it is different that Mo atoms are found to dissolve in the alpha-Fe matrix of the NdFe10.5Mo1.5 disproportionated products while the PrH2+X rods are enriched with B in the case of Pr13Fe80B7 alloys. No special crystallographic relationship between the recombined NdFe10.5Mo1.5 or Pr13Fe80B7 and its disproportionated products is observed. A preferred nucleation and growth of recombined Pr2Fe14B grains is found while that of recombined NdFe10.5Mo1.5 grains is not. Thus, the final hydrogenation-disproportionation desorption recombination (HDDR) NdFe10.5Mo1.5NX powder is isotropic while the HDDR Pr13Fe80B7 powder has a strong anisotropy under the same HDDR treatment conditions. In the end, the formation of anisotropy in the HDDR Pr13Fe80B7 and NdFe10.5Mo1.5NX powders is discussed. (C) 2006 American Institute of Physics.