ON THE FORMATION OF NANOCRYSTALS IN THE SOFT-MAGNETIC ALLOY FE73.5NB3CU1SI13.5B9

Studies were conducted on alloys of atomic mass composition Fe73.5Nb3C u1Si13.5B9 and Fe76.5Cu1Si13.5B9 TEM studies demonstrated that Fe-rich nanocrystals precipitated from the amorphous starting materials exhib ited the DO, structure from very early in the transformation process. This result was corroborated by extended X-ray absorption fines struct ure (EXAFS) studies which showed evidence of ordering in the Fe-rich p recipitates from early in the transformation process. EXAFS studies al so showed that Cu clusters with near-f.c.c. structure were present fro m very early stages of the crystallization process. A model is propose d which describes the role of the Cu clusters as catalyzing nucleation of the DO3 crystallites by providing a low energy interface upon whic h the activation energy for nucleation of the DO3 phase is lowered. (C ) 1998 Acta Metallurgica Inc.