Influence of deformation and annealing twinning on the microstructure and texture evolution of face-centered cubic high-entropy alloys

Abstract

The influence of the physical mechanisms activated during deformation and annealing on the microstructure and texture evolution as well as on the mechanical properties in the equiatomic CoCrFeMnNi high-entropy alloy (HEA) were investigated. A combination of cold rolling and annealing was used to investigate the HEA in the deformed, recovered, partially recrystallized, and fully recrystallized states. Detailed microstructure and texture analysis was performed by electron backscatter diffraction, transmission electron microscopy, and X-ray diffraction. The mechanical properties were evaluated using uniaxial tensile testing. A specific focus of this investigation was put on studying the influence of deformation and annealing twinning on the material behavior. It was substantiated that during cold rolling deformation, twinning facilitates the transition from the Cu-type to the Brass-type texture, whereas annealing-twinning leads to a strong modification of the texture formed during recrystallization. The formation of specific twin orientations and the randomization of the recrystallization texture were proven by experiments as well as by cellular automaton simulations. During tension of the cold-rolled and annealed material high work-hardenability was observed. We attribute this behavior primarily to the dominance of planar dislocation slip and reduced tendency for dynamic recovery, since deformation twinning was observed to activate only in the non-recrystallized grains and thus, contributed minimally to the overall plasticity. The correlation between deformation/annealing twinning and the microstructure evolution, texture development, and mechanical properties was discussed in detail.