Influence of composition and as-cast structure on the mechanical properties of selected high entropy alloys

Abstract

The paper investigates the influence of several alloying elements (Al, Mn, Cu, Ti and Si) and the typology of the as-cast structure on the mechanical properties of high entropy alloys. A theoretical criteria analysis was carried out on the Al–Cr–Cu–Fe–Mn–Ni, Al–Cr–Co–Fe–Ni–Ti, Al–Cr–Fe–Mn–Ni and Al–Cr–Cu–Fe–Mn–Ni–Si alloy systems to select appropriate compositions for application requirements. The alloys were prepared by induction melting and were cast in copper mold. As-cast samples were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction and mechanical analyses. The experimental results partially validated the criteria predictions. Alloys with higher Al content presented most predominantly BCC type phases. Ti and Cu were found enriched in the interdendritic area. Si influenced greatly the as-cast morphology of the dendrite structure. The substitution of Co with Mn generated a significant improvement of the mechanical properties. A composition-structure-properties correlation was described in the paper. The morphology of the as-cast structure had a strong impact on the final properties of the alloys. The Al–Cr–Fe–Mn–Ni alloy showed the best overall characteristics, with a hardness of 412 HV and a compressive strength of 895 MPa.