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+x B 7¹x P 9 Cu 0.7 (x = 0 to 2.5 at%) amorphous alloys were thermodynamically assessed using ThermoCalc 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 Curich 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.

Combined machine learning and CALPHAD approach for discovering processing-structure relationships in soft magnetic alloys

“…In addition, composition variations and processing parameters (e.g., heat treatment schedule) play an integral role in modeling the microstructure(s) responsible for achieving desired properties, where optimizing processing parameters along with composition remains a challenging task. 21 As an alternative to costly experimentation, the CALPHAD approach allows for investigating the effect of composition variations and heat treatment on the size distribution and volume fraction of the phase(s) that are responsible for optimal or desired properties; indeed, it has been used for studying soft magnets containing amorphous phases [22][23][24] using the commercial software Thermocalc. 25 Recent studies indicate that simulations based on CALPHAD 26,27 are in need of efficiency improvements if they are to be used for optimization of the composition and heat treatment schedule.…”

Fe-Si-B-P-C-Cu nanocrystalline soft magnetic powders with high B s and low core loss

“…4 The nanocrystalline structure of NANOMET is developed by annealing amorphous state of precursor samples. The nanocrystallization mechanism of "NANOMET " has been reported in by Takeuchi, et al 5 and Sharma, et al 6 Presently, most NANOMET samples are in the form of ribbon which are produced by a melt spinning method. 7 This technique is reliable to obtain good-quality amorphous precursors because of its high quenching rate.…”