Phase formation and magnetic properties of high-entropy metallic glasses in (Fe, Co, Ni)-P-B alloy system with non-equiatomic ratio

Abstract

In this paper, a series of Fe25+2xCo27.5-xNi27.5-xP14B6 (x = 0, 2.5, 5, 7.5 and 9) high entropy alloys (HEAs) were fabricated via melt-spinning and copper-mold casting, and their phase formation, thermal stability and magnetic properties were investigated. It was found that different phase structures were formed in this alloy system, depending on the variation of composition and cooling rate (Ra). Either a single amorphous phase or multiple phases containing solid-solution phase + compound phase complex were formed in these HEAs depending on Ra. Meanwhile, for Fe30Co30Ni30P7B3 alloy, only a simple solid-solution phase was formed under the fabrication of this work, indicating its insensitivity to Ra. This phenomenon provides a clue to the selection of the desirable phase structure and tailoring magnetic properties by adjusting the composition and Ra. Among this present alloy system, Fe25Co27.5Ni27.5P14B6 alloy ribbon exhibits the lowest coercivity (Hc) of 1.42 A/m, while Fe43Co18.5Ni18.5P14B6 alloy ribbon has the highest magnetic saturation (Bs) of 1.0 T. For Fe30Co30Ni30P7B3 alloy, the Hc decreases from 429.84 A/m to 114.50 A/m by rapid solidification. This work suggests a new route to overcome the restrictions of compositional design by equiatomic ratio to improve soft magnetic properties of HEAs in a wide compositional space.