Effect of pre-deformation on the activation stress of {10–12} twinning in Mg–3Al–1Zn alloy

Abstract

Wrought magnesium and Mg alloys are characterized by a strong basal texture and several slip and twin modes activated at room temperature. These modes interact with each other, and the obstacles on each system associated with other deformation systems are empirically modeled via latent hardening coupling coefficients. {101‾2} tension twinning can be easily and largely activated, causing severe mechanical anisotropy and dramatic texture change. Twin nucleation and growth can also be influenced by slip-induced dislocations. To investigate how dislocations and twins affect {101‾2} twinning, a rolled magnesium alloy AZ31 was pre-deformed along different directions and reloaded in in-plane compression at room temperature. Elasto-visco-plastic self-consistent simulations including twinning, detwinning and secondary twinning show that the critical resolved shear stress for {101‾2} twinning is strongly increased by previous twins, moderately enhanced by basal and pyramidal slips, but additional prismatic dislocations have no effect on twinning. The present experiments and simulations demonstrate that latent hardening for {101‾2} by slip modes is much less than self-hardening.