Effects of different Al contents on mechanical properties and high temperature oxidation resistance of AlxCoCr0.6NiV0.6 high entropy alloy

Abstract

High-entropy alloys with a single-phase FCC structure are widely employed as structural materials due to their excellent ductility and plasticity. Nevertheless, the strength and oxidation resistance of single-phase FCC alloys remain inadequate. Conventional methods for enhancing strength often compromise plasticity, rendering them unsuitable for engineering applications. This study presents a strategy for the preparation of CoCrNi-based AlxCoCr 0.6 NiV 0.6 alloys, characterized by unequal atomic ratios and high entropy, incorporating aluminum and vanadium. Short-range order was observed in each alloy composition, varying in size and crystal plane families. At an aluminum content of x = 0.85, both FCC and BCC dual phases were present in the alloy. The heterogeneous structure and dual-phase presence significantly enhanced the strength and high-temperature oxidation resistance of the high-entropy alloy. The yield strength of the high-entropy alloy increased from 235 MPa to 974 MPa, while the oxide layer thickness decreased from 37.5 μm to 8.3 μm, representing a reduction of 77 %. This study provides a method for adjusting the cross-scale heterostructures in high-entropy alloys (HEAs) and guides the design of CoCrNi-based HEAs with high strength, high ductility, and excellent antioxidant properties. • By adjusting the content of Al element, the control of cross-scale heterostructure is successfully realized. • The alloy is transformed from single-phase FCC to FCC+BCC phases with addition of Al element. • The heterogeneous structure and dual-phase structure improve the yield strength and hardness of the alloy. • The synergistic effect of Al and Cr can improve the high temperature oxidation resistance of the alloy.