Effect of additions on the crystallization process, structure, and magnetic properties of (NdPr)–Fe–B amorphous ribbons

Abstract

The influence of Zr and Mo additions on the crystallization process, microstructure, and magnetic properties of (Nd0.75Pr0.25)12Fe82B6 amorphous alloy ribbons has been studied. Results show that the addition of 3 at. % of either Zr or Mo refines the grains for the optimally annealed alloys, which enhances the intergrain exchange coupling between the RE2Fe14B and the hard magnetic properties. The effect of Zr is, however, superior to that of Mo. Analysis of the crystallization kinetics for the three alloys, investigated by DTA, shows that the activation energy for crystallization Ec(x) for the basic (Nd0.75Pr0.25)12Fe82B6 alloy remains almost constant with increasing crystal fraction x, whereas for both the Mo- and Zr-containing alloys Ec(x) increases gradually with x giving a reduced crystal growth rate consistent with the observed grain refinement. The increase in Ec(x) with x, is larger for the Zr-doped alloy than for the Mo counterpart, which is in accord with the more refined grains and the larger enhancement of Br and (BH)max for the former alloy.