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

In this study, Al0.2Co1.5CrFeNi1.5Ti0.3 high-entropy alloys (HEAs) that contain gamma matrix phase and gamma' 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 super alloys. The gamma/gamma' microstructure in the recrystallized area is much coarser than the spherical gamma' embedded in the gamma matrix, thus leading to the reduction of the gamma/gamma' 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 degrees C just below the gamma' 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 degrees C, which is higher than that in nickel-based superalloys, due to the sluggish diffusion, which would lower the mobility of GB. (C) 2017 Elsevier B.V. All rights reserved.