Effect of cellular structure on the mechanical property of Al0.2Co1.5CrFeNi1.5Ti0.3 high-entropy alloy

Abstract

In this study, Al0.2Co1.5CrFeNi1.5Ti0.3 high-entropy alloys (HEAs) that contain γ matrix phase and γ′ precipitates were heavily deformed and then annealed at different temperatures. Cellular structures were incubated and grown in a shear band below recrystallization temperature. These cellular structures, which are also referred to as discontinuous precipitation, were observed in some nickel-based superalloys. The γ/γ′ microstructure in the recrystallized area is much coarser than the spherical γ′ embedded in the γ matrix, thus leading to the reduction of the γ/γ′ interface and degradation of the precipitation hardening effect. However, results show that these structures can be eliminated by a slow cooling process, as demonstrated in this study. Annealing treatment at 1000 °C just below the γ′ solvus for different durations shows fall-first-and-rise-later hardness, which is due to the dissolution of the precipitates into the migrating grain boundary (GB) caused by static recrystallization, and then subsequently reprecipitates behind the moving boundary. However, this effect on the HEAs is shown at an annealing temperature of 1000 °C, which is higher than that in nickel-based superalloys, due to the sluggish diffusion, which would lower the mobility of GB.