CRYSTALLIZATION BEHAVIOR OF MELT OF Nd-Fe-B-BASED NANOCOMPOSITE PERMANENT MAGNETIC ALLOYS DURING RAPID SOLIDIFICATION

摘要

Rapid solidification process of Fe_3B/Nd_2Fe_(14)B-type alloys has been studied in order to obtain better understandings of the "direct" process in which a nanocomposite structure is formed during the rapid solidification of a melt. A conceptual continuous-cooling-transformation (CCT) diagram of crystallization has been proposed for a Fe_3B/Nd_2Fe_(14)B-type magnet alloy for the case of relatively slow cooling rates of the order of 10~5 K/s. The critical cooling rate for crystallization of Fe_3B has been determined to be 2x10~5 K/s. Effects of influential elements such as Cr and Cu on the crystallization kinetics during rapid solidification have been also studied and discussed. It is suggested that the concept of the CCT diagram is a powerful and useful tool for understanding, controlling and designing the process and microstructure of nanocomposite permanent magnets obtained via rapid solidification processes.