Structural and magnetic studies of the nanocrystalline Nd-Fe-B-Nb alloy ribbons

摘要

A detailed studies of the phase constitution, microstructure and magnetic properties of the nanocrystalline Nd_(9.2)Fe_(61.64)B_(21.16)Nb_8 alloy ribbons, are reported. It was shown that the rapidly solidified ribbons have partially amorphous structure and soft magnetic properties in the as-cast state. The heat treatment at temperatures higher than 923 K led to the growth of the hard magnetic Nd_2Fe_(14)B phase and the metastable Nd_2Fe_(23)B_3 phase. The M?ssbauer confirmed that during annealing of the samples at temperature higher than923 K the paramagnetic Nd_(1+ε)Fe_4B_4 phase was also formed. The microstructure consisting of mixture of constituent phases was observed with transmission electron microscopy (TEM). Furthermore, with increasing annealing temperature the decrease of the saturation polarization Js was observed. The maximum values of coercivity _JH_c= 1175 kA/m was obtained for a sample annealed at 1023K However, annealing at 1003 K resulted in the improvement of remanence polarization J_r = 0.35 T and the maximum energy product(BH)_(max) = 21 kJ/m~3.