Microstructural characterization of an α-Fe/Nd₂Fe₁₄B nanocomposite magnet with a remaining amorphous phase

The microstructures of a Nd₈Fe_76.5Co₈B₆Nb₈Cu _0.5 nanocomposite magnet have been investigated by transmission electron microscopy and three-dimensional atom probe microanalysis. The ribbon prepared by the single roller melt-spinning process under an optimal cooling rate was partially crystallized, being composed of α-Fe, Nd₂Fe₁₄B, and the intergranular amorphous phase. The volume fraction of the Nd₂Fe₁₄B phase increases by annealing at 740 °C for 3 min, but a small amount of amorphous phase remains in the intergranular region. Atom probe results show Nb and B are significantly enriched in the remaining amorphous phase, which would be the reason for the high thermal stability of the remaining amorphous phase. Cu atoms are dissolved in the Nd₂Fe₁₄B phase during solidification, and they do not have much influence on the microstructural evolution.