Optimizing the Manufacturing Process Control of Si-Based Soft Magnetic Composites

This study attempts to enhance the formability and electromagnetic properties of Fe-Si-based soft magnetic composites via process parameter optimization. Two silicon compositions (5.0 and 6.5 wt.%) were examined to determine their influence on density, internal stress, microstructure stability, and magnetic properties using a factorial design comprising 96 different condition combinations. A Pearson correlation analysis revealed a negative relationship between Si content and formability, while magnetic permeability increased with higher Si content. The 5.0 wt.% Si samples exhibited superior density (7.42 g/cm3 vs. 7.28 g/cm3), uniform microstructure, and coating stability. Conversely, the 6.5 wt.% Si samples achieved better permeability (126 at 10 kHz) than 5.0 wt.% Si samples but exhibited higher internal stress, uneven compaction, and thicker insulation layers (~400 nm vs. <10 nm). Scanning electron microscopy and transmission electron microscopy analyses identified necking and damage to the insulation layer. X-ray diffraction verified the stability of the Fe1.6Si0.4 phase after the forming and annealing processes. Secondary molding temperature exhibited the most significant impact on densification, and annealing generally degraded the quality factor (Q-factor). The highest Q-factor value (7.18 at 10 kHz), indicating lower core loss, was observed in the 5.0 wt.% Si samples without annealing.