The effect of annealing on mechanical properties of selective laser melted CoCrNi medium-entropy alloy

Abstract

The mechanical properties were evaluated in the selective laser melted CoCrNi medium-entropy alloy after the annealing at 800 °C. The as-selective laser melted sample delivered the yield strength of 820 MPa, the ultimate tensile strength of 1090 MPa and the fracture strain of 34%, While corresponding value for annealed sample at 800 °C for 4 h was 630 MPa, 870 MPa and 42%, respectively. High density dislocation induced high strength of as-selective laser melted sample, and higher ratio of the low-angle grain boundaries in sample annealed at 800 °C for 1 h impeded the dislocation movement and improved the strength. Moreover, high density dislocation and phase transformation from a face-centered cubic phase to a hexagonal close-packed phase in better recrystallization sample annealed at 800 °C for 4 h synergistically induced strength-ductility trade-off.