Hot deformation behavior and processing map of a Sn0.5CoCrFeMnNi high entropy alloy with dual phases

Abstract

The hot compressive deformation behavior of a cast Sn0.5CoCrFeMnNi high-entropy alloy composed of dual phases, an FCC solid solution phase and a MnNiSn-rich ordered FCC phase (with a volume fraction of 30%), was investigated in temperature and strain rate ranges of 1023–1248 K and 10-3–10 s−1, respectively. During hot deformation, the MnNiSn-rich phase with a relatively low melting temperature (1297 K) underwent a significantly higher degree of dynamic recrystallization (DRX) than the FCC solid solution phase. Continuous DRX occurred in the FCC solid solution phase, but it was pronounced only at the highest temperature of 1248 K. The Sn0.5CoCrFeMnNi alloy exhibited dislocation climb creep at low strain rates and high temperatures and power-law breakdown at high strain rates and low temperatures. The flow stresses of Sn0.5CoCrFeMnNi were notably lower than those of CoCrFeMnNi, though they shared similar deformation mechanisms, by a factor of 0.37–0.71, and this could be explained by the rule of the mixture model considering the contribution of the FCC solid solution phase and the MnNiSn-rich phase to the total deformation rate under the isostress condition. Compared to the Al element in Al0.5CoCrFeMnNi, the Sn element is anticipated to create a larger atomic size misfit in Sn0.5CoCrFeMnNi but promote less viscous glide (solute drag) creep·. The analysis for explaining this reason was conducted from the perspective of factors that affect solute drag creep and breakaway stresses of dislocations from the solute atmosphere.