Compositional Design and Microstructural Tuning of Fe–Si–Co Soft Magnetic Alloys with Enhanced Performance

Abstract

The growing demand for high-efficiency and low-loss energy conversion and transportation techniques urges the development of advanced Fe–Si based soft magnet alloys. Simultaneous achievement of low coercivity (Hc) and large saturation magnetization (Ms) however, remains challenging. In this study, soft magnetic alloys with the composition Fe82–xSi18Cox (x = 0, 4, 8, 12, 16, and 20 at.%) have been designed followed by microstructural tuning. The Co incorporation results in initially decreased Hc followed by increment due to reduced magnetocrystalline anisotropy and increased saturation magnetostriction from negative to positive values of the alloys. Meanwhile, the Ms raises with subsequent reduction, which origins from competitive mechanisms of increased average moment of Fe atoms and decreased average moment of Co atoms according to first principles calculations. Microstructural evolution during annealing of the Fe70Si18Co12 with synergistically optimized Hc and Ms has been revealed, with the A2 and B2 phases transforms into the DO3 phase after elevated-temperature annealing. The growth of the DO3 phase deteriorates the Hc due to its pinning effect on the domain wall movement, which results from the magnetization discontinuity between the DO3 ordered phase and the A2 matrix.

Keywords: Fe-Si-Co alloy, Compositional design, Microstructural evolution, Magnetic domains, Magnetic properties