Preparation of Fe-Si-Ni soft magnetic composites with excellent high-frequency properties

Fe-Si-Ni powders were firstly prepared into soft magnetic composites (SMCs) by ball milling, surface passivation and subsequent compaction. The morphology, phase composition, and magnetic properties of the Fe-Si-Ni powders and their high-frequency performance as SMCs were investigated. The Fe-Si-Ni powders, with saturation magnetization (Ms) of 254.40 emu/g after annealing, were milled down to particle sizes ranging from 40 μm to 150 μm. Surface passivation of the powders was carried out with 0.2-1.0 wt% phosphoric acid solution prior to compaction. Evolution of the high-frequency properties for the Fe-Si-Ni SMCs with the passivator concentration and the molding pressure was studied. With optimized preparation parameters, high saturation flux density (Bs) of 1.23 T, stable permeability, and superior dc-bias property with a percentage permeability above 70% while H=50 Oe were achieved for the Fe-Si-Ni SMC. Minimum core loss (285 mW/cm3) was also measured at 50 kHz for Bm=50 mT.