Co-optimizing magnetic properties and thermal stability of high Bs nanocrystalline alloys with critical formability

Abstract

Abstract The magnetic properties and thermal stability of the Fex(Si2B11P3C1)(99.25-x)/17Cu0.75 (x = 80–86 at.%) nanocrystalline alloys were systematically investigated in this study. It was found that an exceptional combination of high Bs and low Hc can be obtained for the Fe84.5 alloy with a critical formability after annealing in a large temperature-time window. The decrease of Fe content leads to a high formability for the low Fe content alloys (≤83 at.%), but at the sacrifice of Bs, soft magnetic properties and thermal stability. For the Fe86 alloy with excessive Fe content, the precipitation of preformed α-Fe grains in the as-quenched precursors will significantly deteriorate the magnetic softness due to the formation of non-uniform nanostructure with coarse α-Fe grains after annealing. The excellent magnetic properties and thermal stability of the high Fe content alloys with critical formability are attributed to the formation of high number density of fine α-Fe grains in the amorphous matrix, which results in an enhanced soft-impingement and competitive effects. These results will provide a new understanding and strategy for balancing the Bs-formability trade-off as well as enhancing the thermal stability, which are the most important obstacles for the industrial production of high performance nanocrystalline soft magnetic alloys.