Tailoring the strength and ductility of Al0.25CoCrFeNi high entropy alloy through cryo-rolling and annealing

Abstract

FCC-structured Al0.25CoCrFeNi high entropy alloy (Al0.25 alloy for short) was melted and cryo-rolled. The influences of annealing temperature (800 °C, 1000 °C, 1200 °C) on microstructural evolution and mechanical properties were investigated. The results suggested the synchronous enhancements in strength and ductility were obtained in the cryo-rolled Al0.25 alloy annealed at 1000 °C with fully recrystallization and B2 phase precipitation. TEM studying on the deformation behavior of this sample revealed that a laminated HCP phase was transformed from FCC phase during the tensile deformation at ambient temperature, which served as the media of twinning. The outstanding improvements in mechanical properties benefited from the contributions of twin-induced plasticity (TWIP) and phase transformation plasticity (TRIP). In addition, the order of recrystallization and the precipitation/dissolution of B2 phase for the cryo-rolled Al0.25 alloy during annealing process was tried to be clarified, which provided the guideline to tailor the mechanical properties of this alloy.