NANOCRYSTALLINE STRUCTURAL EVOLUTION IN FE90ZR7B3 SOFT-MAGNETIC MATERIAL

Primary crystallization process of an Fe90Zr7B3 amorphous alloy has be en 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 al most completely rejected from the alpha-Fe phase, but some amount of B remains dissolved in the alpha-Fe phase. The as-quenched alloy is amo rphous possibly with the median range order (MRO) structure. Unlike pr eviously published results, no evidence for compositional decompositio n prior to the crystallization reaction was found. This suggests that the crystallization progress by the nucleation and growth mechanism, a nd that redistribution of Zr and B from the crystallized phase to the amorphous matrix controls the grain growth. In fact, during the nuclea tion and growth stage, enrichment of Zr was found in front of the grow ing interface of the alpha-Fe particles, suggesting that the grain gro wth was controlled by the diffusion of Zr.