Cyclic deep cryogenic treatment enables improved mechanical properties and residual stress in additively manufactured CrCoNi medium-entropy alloy

Here, we report the effect of cyclic deep cryogenic treatment (CDCT) cycles on the microstructure, mechanical properties, and residual stress of laser directed energy deposited CrCoNi medium-entropy alloy. Increasing CDCT cycles can increase the tensile strength and compressive residual stress (CRS) of the alloy, which can be ascribed to the repeated activation of visco-plastic deformation during the CDCT process that results in increased CRS and formation of dense dislocations, twins, and stacking faults within alloy. During deformation, these CDCT-induced crystalline defects enhance resistance to dislocation slip, and activate the dynamic Hall-Petch effect earlier, thereby realizing strength-ductility synergy. It was expected that this work can provide new insights to improve the performance of additive manufactured alloys and thus extend their industrial applications.