The influence of the kinetics of the hydrogenation of Nd-Fe-B alloys on hydrogen distribution in the alloy phases

摘要

We present results of experiments on hydrogenation of Nd_(16)Fe_(75.8)B_(8.2) controlled by two parameters: the amount of hydrogen and the rate of feeding the sample with hydrogen at low pressures. By proper combination of these parameters four different schemes for the hydrogenation process were generated: (1) selective hydrogenation of the Nd-rich phase, (2) hydrogenation of the Nd-rich phase followed by diffusion of hydrogen into the Nd_2Fe_(14)B phase, (3) simultaneous partial hydrogenation of both phases, (4) simultaneous complete hydrogenation of both phases For the first two cases the results of measurements of equilibrium pressure versus hydrogen concentration at room temperature are presented in the form of a p-c diagram with three phase regions: (1) Nd+NdH_y+Nd_2Fe_(14)B, (2) NdH_y +Nd_2Fe_(14)B+Nd_2Fe_(14)BH_(x<2.7), (3) NdH_y+Nd_2Fe_(14)BH_(x>2.7)