Twinning susceptibility of CrCoNi medium entropy alloy to cryogenic temperature during asymmetric rolling

Abstract

In this study, the CrCoNi medium-entropy alloys (MEA) were processed by asymmetric rolling (298 K) and asymmetric cryorolling (ACR) (173 K and 83 K), respectively. During the rolling process, as the strain increased (from 50% to 80% reduction), the dislocation distribution inhomogeneity intensified. Meanwhile, the variation of twinning in different systems was more prominent. The cryogenic temperature promoted the inhomogeneity of the structure in the CrCoNi MEA, allowing dislocation cells and dislocation tangling zones to generate at lower strains. And the twinning susceptibility to temperature was more notable than that to strain. Secondary twins, and high-density stacking faults were found in the 173 K ACR CrCoNi MEA at low strain. And tertiary twins were found in the 83 K ACR CrCoNi MEA. It can be found from the experimental results that the improvement effect of the cryogenic environment during rolling on the mechanical properties of the CrCoNi MEA was greater than that of the increase in reduction (50%–80%). Asymmetric cryorolling shows a more efficient strengthening influence on CrCoNi MEA subjected to smaller deformation.

Keywords

• Medium-entropy alloy
• Asymmetric cryorolling
• Twinning
• Cryogenic temperature