Compositionally Engineered Thermal Stable Nanocrystalline Fe-Si-B Soft Magnetic Alloys Via Synergistic Niobium and Phosphorus Alloying

Abstract

The development of advanced soft magnetic materials exhibiting exceptional thermal stability is crucial for realizing next-generation energy-efficient technologies and achieving global carbon neutrality.  This research delves into the microstructure evolution and magnetic properties of a specifically designed Fe82.5Si9.1B1.49Nb5.51Cu1.38P0.02 alloy, exploring its response to various annealing temperatures.  The findings reveal that the precipitated α-Fe(Si) nanocrystalline phase exhibits exceptional thermal stability, maintaining a consistent grain size of approximately 20 nm over a broad annealing temperature range from 673 K to 823 K, far exceeding the stability window of conventional nanocrystalline alloys.  This exceptional stability is attributed to the synergistic effect of niobium and a strategically incorporated, minute addition of phosphorus, which plays a crucial role in stabilizing grain boundaries and impeding grain growth.  Optimal annealing parameters result in good soft magnetic properties, including a saturation magnetization of 1.13 T and a coercivity of 2.1 A/m.  These results not only provide fundamental insights into the compositional design principles for thermal stable nanocrystalline magnets but also offer a new materials platform for high-performance applications in energy conversion and electromagnetic devices.

Keywords: Nanocrystalline materials, Soft magnetic properties, Thermal stability, Grain size control, Microstructure