A novel high-strength and high-ductility CoCrNi medium entropy alloy by Ti/Mo co-doping

Abstract

• A novel alloy design strategy was proposed for FCC-structured CoCrNi-based MEA with outstanding strength-ductility balance. • CoCrNi-based HEA with the dual-precipitates structure prepared by Ti/Mo co-doping. • Precipitation of the L1 2 phase and σ phase by annealing at 950 °C with 1 h. Precipitation strengthening has become the property-tuning method of engineering materials owing to its excellent strengthening effects. In this study, Ti and Mo elements were added to CoCrNi medium entropy alloy (MEA), and dual-precipitates were prepared by mechanical heat treatment. Transmission electron microscopy (TEM) and selected-area electron diffraction (SAED) analyses show that the dual-precipitates are L1 2 and σ phases, which was enriched with Ni, Ti and Cr, Mo elements, respectively. The dual-precipitates in our MEA lead to a promising property with yield strength of 910 MPa and ultimate tensile strength of 1260 MPa with elongation to fracture up to 31%. This work presents a method which by forming various types of ordered intermetallic in MEA to prepare precipitation-strengthened MEA.