Recombination of the Nd2Fe14B phase after reactive milling under hydrogen of a Nd-Fe-B powder

Mechanical milling under reactive hydrogen atmosphere of a Nd-Fe-B powder, followed by vacuum annealing up to 600 degrees C, was achieved. Both as-mil led and annealed powders were investigated by X-ray diffraction and Mossbau er spectrometry. During reactive milling, the Nd2F14B phase disproportionat es into neodymium hydrides (NdH2+/-x) poorly crystallized alpha-Fe and an a morphous Fe-B phase. Upon annealing, hydrogen desorbs from the neodymium hy dride and this is followed by the recombination of the Nd2Fe14B phase. The recombination temperature was found to be 520 degrees C. The recombination reaction is incomplete, likely due to oxygen contamination, as neodymium ox ides, alpha-Fe and Nd1.1Fe4B4 phases are detected in the powder annealed at 600 degrees C. (C) 2000 Elsevier Science B.V. Ail rights reserved.