Enhancing strength-ductility synergy in a casting non-equiatomic NiCoCr-based high-entropy alloy by Al and Ti combination addition

A non equiatomic Ni3.5Co3Cr1.5 medium-entropy alloy (AT0) with a single-phase face-centered cubic structure (FCC) directly obtained by arc-melting shows the low yield strength of 147 MPa, ultimate tensile strength of 447 MPa and large total elongation to fracture of 78.8%. By doping Al and Ti, the as-cast (Ni3.5Co3Cr1.5)(90)Al5Ti5 high-entropy alloy (AT5) exhibits enhanced strength-ductility synergy. Compared to AT0 alloy, the yield strength of AT5 alloy increases more than fivefold to 792 MPa, ultimate tensile strength doubles to 1004 MPa, and still remaining a high elongation of 38.2%. The apparent increase in strength can be attributed to uniformly distributed, high-content, conherent (Ni,Co)(3)(Al,Ti)-type nanoprecipitates formed in FCC matrix. The formation of various dislocation substructures and crossed stacking faults (SFs) with Lomer-Cottrell locks during tensile deformation is responsible for strain hardening of AT5 alloy. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

By doping Al and Ti, the high-entropy alloy exhibits enhanced strength-ductility synergy with uniformly distributed, high-content nanoprecipitates. The formation of various dislocation substructures and crossed stacking faults contributes to the strain hardening of the high-entropy alloy.