A unique Fe-based soft magnetic alloy and its magnetic softening mechanism

Fe-based amorphous alloys with good glass-forming ability (GFA), superior soft magnetic properties, low cost, and a wide heat treatment window have long been pursued in the field of soft magnetic materials due to their importance for mass production and broad applications. In the present study, by strategically adjusting the composition of a low-cost Fe-Si-B-P-Cu-C alloy, we achieved a saturation magnetization (Ms) of approximately 186 emu/g and a coercivity (Hc) of about 6 A/m for the Fe82.5 alloy with a good GFA. Specifically, the limited Cu content and suitable contents of metalloid elements played pivotal roles in enhancing the nuclei barrier and stabilizing the amorphous matrix. This, in turn, facilitated the formation of a finely uniform nanocrystalline structure dispersed within the amorphous matrix, enhancing soft magnetic properties during annealing. Notably, this magnetic softening behavior occurred at a lower heating rate. Structural characterizations revealed that a transient metalloid-rich shell and a stable amorphous matrix contributed to the slow growth of the alpha-Fe (Si) during prolonged isothermal annealing. This is in contrast to the agglomeration of small nanograins into larger clusters at high heating rates, which enhances the versatility and potential applicability of the alloy. The successful development of this novel nanocrystalline alloy offers promising guidance for addressing the challenges associated with the mass production of soft magnetic materials.