Towards strength-ductility synergy in a CrCoNi solid solution alloy via nanotwins

Single-phase face-centered cubic (FCC) medium/high-entropy alloys (M/HEAs) have drawn much attention recently regarding their intriguing mechanical properties such as a good combination of strength, ductility, and fracture toughness. But the yield strength levels of these alloys are still low as compared to other high strength metallic materials. Here, both static plastic deformation (SPD) and dynamic plastic deformation (DPD) were employed to improve the yield strength of CrCoNi MEA. A very high yield strength of more than 900 MPa was obtained after SPD/DPD. The elongation rates were reduced dramatically after SPD, while a combination of ultrahigh yield strength of 930 MPa with a high elongation of 27% was achieved after DPD. When compared to SPD, a high density of nanoscale deformation twins can be observed inside the grains in the DPD sample, which could be responsible for the outstanding tensile properties after DPD. Our results can provide a new strategy to significantly increase the yield strength of FCC M/HEAs while maintaining a high elongation.