Revealing the microstructural evolution and mechanism during the thermomechanical treatment of polycrystalline CrCoNi medium-entropy alloy

Abstract

It is well-known that recrystallization plays an essential role in tuning the microstructure and grain size for obtaining favorable mechanical properties. However, the recrystallization behaviors are significantly affected by the deformation paths and post heat treatment parameters. In this paper, the recently developed CrCoNi medium-entropy alloy was compressed at 1000 °C with strain rates of 0.01/s, 0.1/s and 1/s, after which, all the compressed samples were annealed at temperatures of 650 °C, 750 °C for 0.5 h and 1 h, respectively. The evolution of grain size and local misorientation as well as annealing twin behaviors were studied in detail using the EBSD technique. A high density of annealing twin boundaries and finer equiaxed grains were obtained after the specimens deformed at slower strain rates and annealed at 750 °C/1 h, in which significant discontinuous static recrystallization occurred. The factors affecting recrystallization behaviors were qualitatively described and the corresponding mechanism of microstructural evolution was discussed in detail.