High strength and ductility of an additively manufactured CrCoNi medium-entropy alloy achieved by minor Mo doping

Abstract

The effect of minor Mo doping on the microstructure and mechanical properties of a (CoCrNi)95Mo5 medium-entropy alloy (MEA) was studied by selective laser melting (SLM) to architect the dislocation-formed sub-grains, ultrafine (Mo, Cr)-enriched μ precipitates and various lattice defects. High strength and ductility were achieved in the as-SLMed (CoCrNi)95Mo5 alloy, where the yield strength, ultimate tensile strength (UTS) and fracture strain were 0.79 GPa, 0.97 GPa and 35.9%, respectively. The superior mechanical properties were associated with the typical hierarchical microstructure that were featured by the high-density dislocations-formed equiaxed sub-grains, the columnar sub-grains separated by low-angle grain boundaries (LAGBs), the fine (Mo, Cr)-enriched μ precipitates and the lattice defects including dislocations, stacking faults (SFs) and Lomer-Cottrell locks (LCs) in the matrix. The results have demonstrated the potential of applying precipitation strengthening in CoCrNi-based MEAs through additive manufacturing to achieve superior mechanical properties.