Correlation Mechanism of Microstructure, Magnetic Domain, and Magnetic Softness of Fe-6.5 wt.%Si Composites with High Saturation

Reducing the low-frequency loss (≤ 1 kHz) of the soft magnetic powder cores (SMPCs) while maintaining high saturation magnetic induction ( B s ) is beneficial to the high efficiency and energy saving of motor applications. Herein, the effects of silicone resin content (SI), compaction pressure, and annealing temperature on the magnetic softness, microstructure, and magnetic domains of Fe-6.5 wt.%Si SMPCs were systematically studied. The SMPCs with 1 wt.% SI content and pressed at 1800 MPa not only have good forming ability but also exhibit low total loss and high B s . According to the loss separation at 1 T and 1 kHz, the hysteresis loss accounts for more than 75% of the total loss. Annealing at 850 °C induces dense and large recrystallized grains with large-angle grain boundaries and easily mobile domain walls, resulting in low hysteresis and total loss. A higher temperature of 950 °C damages the cladding layer and causes direct powder-to-powder contact, which thus slightly increases hysteresis and eddy loss. The correlation between the core loss, microstructure, and magnetic domain provides a reference for the development of high- B s and low-loss SMPCs for high-efficiency motors.