MAGNETIC AND PHASE-TRANSITIONS AND HDDR PROCESSES IN NDFEB-TYPE ALLOYS MONITORED BY ELECTRICAL-RESISTIVITY MEASUREMENTS

Magnetic and phase transitions and the hydrogenation, disproportionati on, desorption, recombination process of NdFeB-type alloys have been i nvestigated by electrical resistivity measurements. The Curie points a nd the temperatures of formation of the liquid grain boundary phase of Nd14.68Dy0.94Al0.62Fe76.47Nb0.5B6.79 and Nd1.56Fe74.9B8Cu1.5 have bee n determined and the kinetics of the disproportionation reaction under hydrogen and the recombination under vacuum at 820-degrees-C of these alloys have been studied for the first time by a technique employing in-situ measurements of the electrical resistivity. Differences in the kinetics of the disproportionation reactions in the two alloys, in wh ich the Nd2Fe14B phase forms Fe, Nd-hydride and Fe2B, can be related t o the effects of alloy composition and initial microstructure.