Martensitic transformation in CrCoNi medium-entropy alloy at cryogenic temperature
Muhammad Naeem, Hao Zhou, Haiyan He, Stefanus Harjo, Takuro Kawasaki, Si Lan, Zhenduo Wu, Yuntian Zhu, Xun‐Li Wang
Abstract
We investigated the in situ deformation behavior of the CrCoNi medium-entropy alloy at a cryogenic temperature of 140 K and compared it with deformation at room temperature. The sample exhibited higher strength and larger ductility at the cryogenic temperature. The CrCoNi alloy remained single-phase face-centered cubic at room temperature, while deformation at 140 K resulted in a martensitic transformation to the hexagonal close-packed structure. The phase transformation, an additional deformation mechanism to stacking faults, twinning, and dislocation slip, resulted in a higher work hardening at cryogenic temperature. The study addresses the structure metastability in the CrCoNi alloy, which led to the formation of epsilon-martensite from the intrinsic stacking faults.