Enhancing the strength-ductility trade-off in C0·1CrMnFeCoNi0.8 high-entropy alloy: A combined experimental and DFT study

As a rapidly emerging class of metallic materials, high-entropy alloys (HEAs) provide the opportunity to develop novel alloys with superior mechanical properties through tackling the long-standing challenges, such as strength-ductility trade-off dilemma. Herein, C-doped CrMnFeCoNi0.8 alloys were produced by vacuum induction melting. The addition of C up to 0.1 at % strengthens the CrMnFeCoNi0.8 alloy without sacrificing ductility. Compared to the base alloy, the yield strength of the C0.1CrMnFeCoNi0.8 alloy was increased by ∼40 % from 240.9 MPa to 334.2 MPa at no reduction in tensile ductility, mainly attributed to the formation of fully coherent carbide precipitates on the grain boundaries. The mechanical properties of the C0.1CrMnFeCoNi0.8 alloy can be further enhanced by annealing. The alloy annealed at 950 °C exhibits a yield strength of 517.8 MPa, an ultimate tensile strength of 914.6 MPa, and an appreciable ductility (20.5 %), achieving an excellent combination of strength and ductility. Furthermore, the influence of C addition on the mechanical properties and electronic structures were explored using density functional theory (DFT) calculations to understand the enhanced strength-ductility synergy in the C0.1CrMnFeCoNi0.8 alloy.