Thermodynamic Assessment of Fe-B-P-Cu Nanocrystalline Soft Magnetic Alloys for Their Crystallizations from Amorphous Phase

Abstract

The crystallization processes of Fe_83.3+xB_7−xP₉Cu_0.7 (x = 0 to 2.5 at%) amorphous alloys were thermodynamically assessed using Thermo-Calc software with TCFE7 database for Fe-based alloys. The analysis of the alloys for a primary crystallization precipitating bcc-Fe revealed metastability among four phases comprising bcc-Fe, two kinds of Fe-based amorphous phases that are rich in Fe-B and Fe-P and crystalline Cu-rich phase. The roles of P and Cu additions to the Fe-based amorphous alloys are thermodynamically interpreted as stabilizing the remaining amorphous phase at the primary crystallization. The dual Fe-rich amorphous phases due to the inclusion of P characterize a heterogeneous amorphous structure of NANOMET family alloys comprising Fe and metalloids mainly and without early-transition metals.