Microstructure and magnetic properties of microalloyed α-Fe/Nd 2Fe 14B nanocomposites

Abstract

The effect of minor elements (Cu, Nb, Zr and/or Ga) on the microstructure and magnetic properties of α-Fe/Nd 2Fe 14B nanocomposites obtained by melt-spinning Nd 8Fe 87B 5 based alloys has been studied by using three-dimensional atom probe and transmission electron microscopy. Cu atoms form clusters prior to the crystallization of amorphous precursors. However, Cu clusters do not act as heterogeneous nucleation sites for the α-Fe crystals; thus, Cu addition is not beneficial for reducing the grain size of α-Fe/Nd 2Fe 14B nanocomposites. On the other hand, Nb is effective in suppressing grain growth while annealing an partially crystallized melt-spun Nb-containing alloy. However, it was not possible to optimize the microstructures and magnetic properties by crystallizing Nb-containing amorphous precursors. The hard magnetic properties with H c=496 kA/m and ( BH) max=134 kJ/m 3 were obtained by adding a small amount of Zr. The coercivity was enhanced by combined addition of Zr and Ga. Zr and Ga atoms are partitioned into the Nd 2Fe 14B phase, and evidence for a slight enrichment of Zr atoms at the α-Fe/Nd 2Fe 14B interfaces has been found.