On the formation of nanocrystals in the soft magnetic alloy Fe73.5Nb3Cu1Si13.5B9

Studies were conducted on alloys of atomic mass composition Fe73.5Nb3Cu1Si13.5B9 and Fe76.5Cu1Si13.5B9 TEM studies demonstrated that Fe-rich nanocrystals precipitated from the amorphous starting materials exhibited the DO, structure from very early in the transformation process. This result was corroborated by extended X-ray absorption fines structure (EXAFS) studies which showed evidence of ordering in the Fe-rich precipitates from early in the transformation process. EXAFS studies also showed that Cu clusters with near-f.c.c. structure were present from very early stages of the crystallization process. A model is proposed which describes the role of the Cu clusters as catalyzing nucleation of the DO3 crystallites by providing a low energy interface upon which the activation energy for nucleation of the DO3 phase is lowered. (C) 1998 Acta Metallurgica Inc.