Cyclic deep cryogenic treatment enables improved mechanical properties and residual stress in additive

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.