Impact of rolling temperature on the deformation structure and mechanical performance of a CrMnFeCoNi high-entropy alloy

Abstract

The impact of warm-rolling at 773 K to 76% and 90% thickness reduction on the microstructure and mechanical properties of an equiatomic CrMnFeCoNi high entropy alloy is compared to material that is cold-rolled and subsequently annealed between 673 and 1173 K. While cold-rolling significantly improves hardness and yield strength, subsequent annealing with increasing temperature improves ductility due to stress-relaxation, recovery, and recrystallization of the elongated grain structure which simultaneously reduces hardness and strength. Compared to the cold-rolled condition, however, annealing at 773 K increases hardness and strength as well as ductility which may be associated with the onset of chemical ordering combined with a lack of the formation of precipitates. Warm-rolling at 773 K, on the other hand, results in partially recrystallized microstructures without mechanical nanotwins. While the 76% deformed material exhibits mechanical properties that are comparable to the cold-rolled and annealed materials, the 90% warm-rolled material shows significantly improved hardness compared to the cold-rolled material, similar strength, but improved plastic failure strains. These properties are associated with the formation of a fine lamellar deformation structure and the onset of the precipitation of Cr-rich particles during rolling. Our results reveal that warm-rolling may enable an efficient pathway to obtain structure-property relationships in HEAs that can otherwise only be obtained in a multi-step processing procedure.