Effect of Grain Size on Critical Twinning Stress and Work Hardening Behavior in the Equiatomic CrMnFeCoNi High-Entropy Alloy

•The uniaxial twinning stress decreases from ∼785 MPa for a grain size d = 6 µm to ∼615 MPa for d = 242 µm, following the hall-petch equation.•The resistance of grain boundaries against slip and twinning is nearly identical. This contrasts with what was reported in the case of pure cu and binary Cu-based alloys.•The estimated CRSS for twinning is 193 ± 10 MPa, assuming a taylor factor of 3.06.•When the sample thickness-to-grain size ratio is only 4, free surfaces affect the work hardening behavior but their influence on the yield and twinning stresses is not significant.•Deformation twinning enhances the work hardening rate only when it is activated well before the generalization of cross slip with the formation of dislocation cells.