Microstructure and Texture Evolution During Thermomechanical Processing of Al0.25CoCrFeNi High-Entropy Alloy

Microstructure and texture evolution was studied in a Al0.25CoCrFeNi high-entropy alloy after cold work and subsequent isochronal annealing treatments. The alloy was synthesized by arc-melting and the resulting ingots were cold rolled up to two different thickness reductions: 50 pct and 80 pct. The alloy was then annealed for 1 hour at 973 K, 1073 K, 1173 K, and 1273 K. The final microstructures were analyzed using X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction and the results were correlated with hardness measurements. The sample reduced by 80 pct recrystallized at a lower temperature than the sample reduced by 50 pct, confirming the influence of the deformation degree on the rate of nucleation and growth of new grains. The recrystallized microstructures revealed equiaxed grains with a high density of twins, which is typical of metals with low stacking fault energy. Twins were also observed in the as-rolled samples, suggesting that twinning precedes shear banding during deformation of this alloy. This accounts for the strength of the {110} < 112 > brass texture component in the cold rolled samples. (C) The Minerals, Metals & Materials Society and ASM International 2019