Twinning and detwinning behaviors of commercially pure titanium sheets

The mechanical behaviors of commercially pure titanium (CP-Ti) sheets under uniaxial and reverse loadings along various in-plane directions are investigated by crystal plasticity modeling together with experiments. The elastic viscoplastic self-consistent (EVPSC) crystal plasticity model, that incorporates an enhanced twinning and detwinning (TDT) scheme to consider multiple twinning modes, is employed for the crystal plasticity modeling. The in-plane anisotropic, the tension-compression asymmetric, and the unique work hardening behaviors of the CP-Ti sheets are ascribed to available deformation mechanisms. In addition to various deformation slips (e.g., prismatic, basal and pyramidal c + a slips), deformation twinning and detwinning of extension ({10 (1) over bar2}) and contraction ({11 (2) over bar2}) twinning modes are deliberated in particular. The effect of the mechanisms on the evolution of the stress strain relation, hardening rate, texture, relativity activities, and twin volume fractions, etc. is explored. It is found that twinning and detwinning of both extension and contraction twins, as well as deformation slips, affect significantly the behaviors of the CP-Ti sheets. The modeling results agree well with the corresponding experiments. The difference of the mechanical behaviors between the two sheets and the difference among various loading conditions are ascribed to the different combination of the operative deformation mechanisms, especially the contribution from twinning and detwinning of extension and contraction twins.