Microstructure and mechanical properties variation with Ni content in Al0.8CoCr0.6Fe0.7Nix (x = 1.1, 1.5, 1.8, 2.0) eutectic high-entropy alloy system

Abstract

Eutectic high-entropy alloys have drawn extensive attention because of their remarkable performance on the combination of strength and plasticity. In this study, a new Al0.8CoCr0.6Fe0.7Nix (x = 1.1, 1.5, 1.8, 2.0) eutectic high-entropy alloy system was designed; the microstructure and mechanical properties variation of alloys with the change in Ni content were investigated detailly. All of four alloys exhibited FCC+B2 dual-phase structure, while the volume fraction of FCC phase increased from 44% to 90% with an increase in Ni content. Meanwhile, the microstructure of alloys variated from an irregular dendrite morphology to a lamellar eutectic microstructure, and finally to a hypoeutectic microstructure composed by primary FCC phase and the rest eutectic mixture. Accordingly, the yield strength of alloys decreased from 625 MPa to 415 MPa, and the total elongation increased from 7.4% to 21.8%. The Al0.8CoCr0.6Fe0.7Ni1.5 alloy displayed a nano-scale lamellar eutectic microstructure and exhibited a relatively good combination of strength and plasticity in these four alloys, with a yield strength of 490 MPa, a ultimate strength of 980 MPa and a total elongation of 14.8%. The findings could contribute to explore HEAs with good combination of strength and plasticity and promote the applications of high-entropy alloys in industrial fields.