Crystallization kinetics of amorphous Nd_3.6Pr_5.4Fe₈₃Co₃B₅ and preparation of α-Fe/Nd₂Fe₁₄B nanocomposite magnets by controlled melt-solidification technique

来源期刊：中南大学学报(英文版)2003年第4期

论文作者：杨丽 尚勇

文章页码：280 - 286

Key words：nanocomposite magnet; nanocrystalline alloy ; amorphous alloy

Abstract: The crystallization kinetics of amorphous Nd_3.6Pr_5.4Fe₈₃Co₃B₅and the preparation of α-Fe/Nd₂Fe₁₄B nanocomposite magnets by controlled melt-solidification of Nd_3.6Pr_5.4Fe₈₃Co₃B₅was investigated by employing DTA,XRD, and TEM. The results show that a metastable intermediate phase Nd₈Fe₂₇B₂₄ prior toα-Fe and Nd₂Fe₁₄B phases is crystallized as the amorphous Nd_3.6Pr_5.4Fe₈₃Co₃B₅ is heated to 1 223 K. The crystallization activation energy of α-Fe and Nd₈Fe₂₇B₂₄ phases is larger at the beginning stage of crystallization, and then it decreases with crystallized fractionx for the former and has little change whenxis below 70% for the latter, which essentially results in anα-Fe/Nd2Fe14B microstructure with a relatively coarse grain size about 20-60 nm and a non-uniform distribution of grain size in the annealed alloy. Theα-Fe/ Nd₂Fe₁₄B nanocomposite magnets with a small average grain size about 14 nm and a quite uniform grain size distribution were prepared by controlled melt-solidification of Nd_3.6Pr_5.4Fe₈₃Co₃B₅ at a wheel speed of 20 m·s^-1during melt-spinning. The magnets show a high maximum energy product of (BH)_max = 194 kJ·m^-3, which is nearly twice of that of the nanocomposite magnets made by annealing the amorphous Nd_3.6Pr_5.4Fe₈₃Co₃B₅ precursor alloy.