Nanocrystalline structural evolution In Fe90Zr7B3 soft magnetic material

Primary crystallization process of an Fe90Zr7B3 amorphous alloy has been studied by atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM). It is confirmed that two phases coexist at the stage with optimum magnetic properties, one is the alpha-Fe phase and the other is the amorphous phase enriched with Zr and B. Zr is almost completely rejected from the alpha-Fe phase, but some amount of B remains dissolved in the alpha-Fe phase. The as-quenched alloy is amorphous possibly with the median range order (MRO) structure. Unlike previously published results, no evidence for compositional decomposition prior to the crystallization reaction was found. This suggests that the crystallization progress by the nucleation and growth mechanism, and that redistribution of Zr and B from the crystallized phase to the amorphous matrix controls the grain growth. In fact, during the nucleation and growth stage, enrichment of Zr was found in front of the growing interface of the alpha-Fe particles, suggesting that the grain growth was controlled by the diffusion of Zr.