The effect of Al to high-temperature deformation mechanisms and processing maps of Al0.5CoCrFeMnNi high entropy alloy

Abstract The high-temperature deformation mechanism and processing maps of cast Al 0.5 CoCrFeMnNi that comprises face centered cubic (FCC) and body centered cubic (BCC) phases (where BCC phase is a minor phase) were studied at temperatures in the range of 1023–1323 K and at strain rates in the range of 10 −3 to 10 1 s −1 . During hot compression, the hard BCC phase provided nucleation sites for dynamically recrystallized (DRXed) grains in the soft FCC matrix through particle stimulated nucleation (PSN). Continuous dynamic recrystallization simultaneously occurred with the PSN-induced DRX. As a result, the fraction of DRXed grains was notably higher and the size of the DRXed grain size was considerably smaller in Al 0.5 CoCrFeMnNi than those in the equiatomic CoCrFeMnNi with a single FCC phase. The effect of the BCC phase on the fraction of DRXed grains was especially pronounced at high strain rates (10 s −1 ) in the temperature range between 1173 and 1323 K, which is important for the practical use of cast Al 0.5 CoCrFeMnNi in the hot-working industry. Solute drag creep appeared at low strain rates and at high temperatures as the rate-controlling deformation mechanism due to the presence of Al solutes in the FCC matrix. The activation energy for plastic flow associated with solute drag creep was measured to be 251 kJ/mol. This value most likely represents the activation energy for the interdiffusivity of aluminum solutes in Al 0.5 CoCrFeMnNi. The solute drag creep behavior could be predicted by the Weertman model, indicating that Al 0.5 CoCrFeMnNi behaves similar to a typical class I type solid solution metal alloy. By adding aluminum to CoCrFeMnNi, the hot workability was greatly improved according to the processing maps. The power dissipation efficiency was notably increased, and the flow instability regime decreased in size.