FeCo-based nanocrystalline alloys with excellent soft magnetic properties obtained by high-temperature short-term heat treatment

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The urgent need for materials with high saturation magnetic induction ( Bs ) and low coercivity ( H c) for next-generation high-performance amorphous motors is a critical step toward achieving carbon neutrality. In this study, we focus on the Fe-Co-B alloy system, which is renowned for its high Bs . Through systematic composition design and rapid annealing (RA) heat treatment, we investigated the effects of RA on the microstructure, magnetic domain structure, soft magnetic properties, and bending toughness of the alloy, revealing the evolution laws of nanostructure and properties during the alloy crystallization process. The results demonstrate that the strategy of high-temperature, short-time RA yields the most favorable outcomes. By reaching an extremely high superheat in a short duration, intense composition and energy fluctuations occur, significantly promoting the in-situ uniform nucleation process within the amorphous matrix and forming a highly refined amorphous/nanostructure composite structure. Following rapid heat treatment, the Bs reached 1.96 T, while H c was as low as 5.1 A/m (from M-H curves), and the material retained excellent bending toughness, indicating its potential for application in amorphous motors and electronic devices.