Unique hot deformation behavior and microstructure evolution of a dual FCC-phase CoCrCu1.2FeNi high entropy alloy

The hot deformation behavior and microstructure evolution rule of an as-cast CoCrCu1.2FeNi high entropy alloy composed of two FCC phases were investigated by hot compression tests at temperatures from 973 K to 1223 K and strain rates from 0.001 s-1 to 1 s-1 and electron backscatter diffraction (EBSD) analysis. The results showed that at low temperature and high strain rate, the strain hardening is remarkable. Two optimized hot working regions including (1000-1173 K, 0.04-1 s-1) and (1173-1223 K, 0.001-0.01 s-1) were found in the processing map. Asynchronous dynamic recrystallization (DRX) occurs during hot compression, and the DRX fraction increases with the increase of temperature. At 1223 K/0.001 s-1, the DRX fraction reaches 30.4%, and the fraction of sub-grains reaches 37.6%. At low temperature, especially at high strain rate, two kinds of strong textures are formed in the two phases, and the maximum texture strength decreases with the increase of temperature. The DRX mechanism of CoCrCu1.2FeNi alloy is mainly discontinuous dynamic recrystallization mechanism (DDRX) at low temperature and continuous dynamic recrystallization mechanism (CDRX) at high temperature. The asynchronous DRX of the two phases makes the boundary of FCC1 and FCC2 easier to crack, leading to the formation of hot working defects. (c) 2021 Elsevier B.V. All rights reserved.