Twin-coupled shear bands in an ultrafine-grained CoCrFeMnNi high-entropy alloy deformed at 77K

Abstract

Two different types of shear bands generate in ultrafine-grained (UFG) CoCrFeMnNi high-entropy alloys deformed at 77 K, i.e. commonly-observed low angle grain boundary (LAGB) type and unusual twin-coupled type. Twin-coupled shear bands exhibit a misorientation of 56–67° with the matrix, in contrast to the LAGB shear band with a misorientation of 6–12°. Both annealing twins and deformation twins can act as precursor for twin-coupled shear bands, where dislocation accumulation along twin boundaries can tune the orientation of twin lamella. These observations suggest that twin-coupled shear bands can act as an important plastic carrier in materials deformed under extreme conditions.