Microstructural evolutions of Pr13Fe80B7 alloys during solid HDDR process

Microstructural evolutions of Pr13Fe80B7 alloys during solid hydrogenation disproportionation desorption recombination (HDDR) process is systematically investigated. The results show that the early-disproportionated products of Pr13Fe80B7 alloys are mainly characteristic of rod-like morphology, and the rods are PrH2 while the matrix is Fe. Moreover, all the PrH2 rods have the same crystallographic orientation, and grow with a definite orientation related to the Fe matrix. However, it is notable that no iron boride phase except for NdH2 and Fe is found. With the prolonged disproportionation time, the rod-like disproportionated products coarsen, and the Fe2B come to form. When the disproportionation time is 17 h, the rod-like disproportionation morphology transforms into sphere, and a large amount of Fe2B is found. Subsequent investigations for the recombination show that the recombination reactions start at the boundaries between PrH2 rods and Fe matrix, and the rim-like Pr2Fe14B is formed on the PrH2 rods. Moreover, the recombined PrFeB powder of the rod-like microstructure has strong magnetic anisotropy.