Effect of strain path on microstructure and texture formation in cold-rolled and annealed FCC equiatomic CoCrFeMnNi high entropy alloy

Abstract

The effect of strain path on microstructure and texture formation in an equiatomic CoCrFeMnNi high entropy alloy was investigated. For this purpose, the alloy was cold-rolled to 90% reduction in thickness (total equivalent strain (εeq) ∼2.65) using unidirectional cold-rolling (UCR) and different cross-rolling routes. In the MSCCR route, the samples were rotated by 90° around the ND in between each pass. In the TSCCR(90°) and TSCCR(45°) routes, the samples were deformed by unidirectional rolling to half of the εeq (∼1.3) in the first step and the rest half of the strain (εeq ∼1.3) was imparted after rotation around the ND by 90° and 45°, respectively. The development of deformation microstructures in all the processing routes were characterized by fine lamellar type structure intercepted by inclined shear bands. The TSCCR(45°) processed material appeared to be most prone to shear band formation. The UCR processed material showed brass type texture, while the textures of different cross-rolled materials were featured by different rotated brass components. Upon annealing, the UCR processed material showed the lowest grain size while the highest grain size was observed in the TSCCR(45°) processed material. This indicated greater available nucleation sites in the UCR processed material as compared to the TSCCR(45°) processed material. The differences in annealed grain size was presumably higher due to substructure destabilization and misorientation build-up diminishing the number of potential nuclei in the TSCCR(45°) processed material. The annealing textures of the differently processed materials were featured by the presence of α-fiber (ND//<110>) and absence of preferential nucleation and growth.