Structural Evolution Mechanism of Early-Stage Nanocrystallization of Finemet Amorphous Ribbons

The Finemet alloy is used to make transformers for its excellent soft magnetic property. In order to study its distinctive character, it is essential to clarify the structural evolution mechanism especially in early nanocrystallization. The Fe
_73.5
Si
_13.5
B
₉
Nb
₃
Cu
₁
amorphous ribbons were prepared by single-roller melt-spinning process under argon atmosphere, and then annealed at 350°C, 380°C and 400°C for 10 mins respectively. We conduct the X-ray photoelectron spectrum (XPS) and the atom force microscope (AFM) to investigate the structural evolution mechanism in early nanocrystallization of Finemet. The X-ray photoelectron spectrum present the Cu atoms enrich in the surface and the Nb atoms redistribute to the iron-rich layer following with the increasing annealing temperature. The atomic force micrographs for the annealed specimens present a significant increase in the amount of the clusters and a dramatic drop in their average size. The structure evolution as observed is subjected to the atomic redistribution, which is crucial to the formation of the Cu-enriched clusters. In this paper, we discuss the behavior of different elements and elaborate the transformation of microstructure during the process of atomic migration.