Microstructural evolutions in NdFe_(10.5)Mo_(1.5)N_x and Pr_(13)Fe_(80)B_7 compounds during hydrogenation-disproportionation desorption recombination process

摘要

Microstructural changes of NdFe_(10.5)Mo_(1.5) and Pr_(13)Fe_(80)B_7 compounds during the solid-hydrogenation disproportionation desorption recombination process are investigated in this paper. It is found that the early disproportionated microstructure of NdFe_(10.5)Mo_(1.5) and Pr_(13)Fe_(80)B_7 alloys shows similar rodlike morphology. All the NdH_(2+x) and PrH_(2+x) rods have the same orientation and grow with a definite orientation related to the α-Fe matrix. However, it is different that Mo atoms are found to dissolve in the α-Fe matrix of the NdFe_(10.5)Mo_(1.5) disproportionated products while the PrH_(2+x) rods are enriched with B in the case of Pr_(13)Fe_(80)B_7 alloys. No special crystallographic relationship between the recombined NdFe_(10.5)Mo_(1.5) or Pr_(13)Fe_(80)B_7 and its disproportionated products is observed. A preferred nucleation and growth of recombined Pr_2Fe_(14)B grains is found while that of recombined NdFe_(10.5)Mo_(1.5) grains is not. Thus, the final hydrogenation-disproportionation desorption recombination (HDDR) NdFe_(10.5)Mo_(1.5)N_x powder is isotropic while the HDDR Pr_(13)Fe_(80)B_7 powder has a strong anisotropy under the same HDDR treatment conditions. In the end, the formation of anisotropy in the HDDR Pr_(13)Fe_(80)B_7 and NdFe_(10.5)Mo_(1.5)N_x powders is discussed.