Synthesis of Fe-Co-Ni-(B, Si, C) ferromagnetic high entropy amorphous alloys and their thermal and magnetic properties

Abstract

The ferromagnetic Fe-Co-Ni-(B, C, Si) high entropy alloys (HEAs) with an amorphous structure were prepared by single-roller melt-spinning method and evaluated their thermal and magnetic properties. The single amorphous phase is obtained both the Fe25Co25Ni25(B1−xSix)25 HEAs and Fe75(B1−xSix)25 alloys (x = 0.3, 0.5, 0.7). It was confirmed that the HEAs with x = 0.3 and 0.5 exhibits the glass transition prior to crystallization. On the other hands, the Fe75(B, Si)25 alloys do not show the glass transition. The critical thickness for the amorphous formation is larger than 0.23 mm for the Fe25Co25Ni25(B0.7Si0.3)25 HEA and is approximately 0.10 mm for the Fe75(B0.7Si0.3)25 alloy. Therefore, the HEAs have much larger glass-forming ability than that of the conventional Fe-based amorphous alloys. The similar results were obtained in the Fe25Co25Ni25(B1−xCx)25 HEAs. On the other hand, the amorphous phase could not be obtained for the Fe25Co25Ni25(Si1−xCx)25 HEAs and Fe75(Si1−xCx)25 alloys. It was also confirmed that the saturation magnetization at room temperature of the HEAs is about a half that of the Fe-based amorphous alloys.