Microstructure evolution, magnetic properties and frequency characteristics of Si-rich FeSiBCuNb soft magnetic alloy induced by annealing treatment

The influences of heat treatment on the microstructure, domain structure and magnetic characteristics of the Fe 73.5 Si 15.5 B 7 Cu 1 Nb 3 alloy were investigated. We demonstrated that the as-spun alloy exhibits high amorphous forming ability and good thermal stability with a large annealing interval between the primary and secondary crystallization peaks over 170 °C. Also, the interaction of chemical concentration fluctuations and heterogeneous nucleation is responsible for the nanocrystallization mechanism of alloy. Furthermore, the magnetic structures change from the narrow and zigzag-like branched domains to wide and regular striped domains with increasing annealing temperature, which leads to a decrease in pinning effects. Appropriate magnetic anisotropy introduced by heat-treatment process has effect on the magnetic mechanism and the shape of magnetic hysteresis loops, which adjusts the frequency characteristics. After the optimum annealing, the alloy exhibits the excellent magnetic properties including high Ms. of 135.4 emu/g and low Hc of 0.56 A/m, together with good low-frequency characteristics. • Nanocrystallization mechanism of the Si-rich Finemet amorphous alloy were studied roundly. • High volume fraction, fine, and uniformly distributed nanocrystalline structure was obtained. • Optimal Ta induced wide magnetic domains achieves high Ms., low Hc and high L. • High-temperature annealing introduced anisotropy improves high frequency characteristics.