On the microstructures, phase assemblages and properties of Al0.5CoCrCuFeNiSix high-entropy alloys

• The microstructure, phase assemblage and mechanical properties of the Al0.5CoCrCuFeNiSix alloys were investigated.
• The addition of Si induced a microstructure change from FCC solid solution to BCC solid solution.
• With the additions of Si, the hardness, wear resistance and strength were greatly enhanced.
• The excellent properties came from the changes from FCC to BCC structure and the solution strengthening of Si.

The microstructures, phase assemblages and properties of Al0.5CoCrCuFeNiSix (x = 0, 0.4, 0.8) high-entropy alloys are studied in this paper. Alloy with x = 0 is a simple FCC solid solution. As Si content x increases, alloys are gradually changed from FCC to BCC. As Si content x increases, compressive strength of the alloys increases, while ductility decreases. The parameters representing simple solid-solution formation ability in Al0.5CoCrCuFeNiSix alloys are estimated. The addition of Si destabilizes the FCC structure and introduces the transition from a closed-packed FCC structure to a loose-packed BCC structure to relax the lattice distortion energy due to the smaller radius of Si. The improved mechanical properties of the alloys are attributed to the basic structure changes from FCC to BCC phases and solution hardening mechanism.