Induction of deformation twinning by dynamic strain aging effect: Rate-temperature coupling effect and constitutive modeling

This study focuses on the rate-temperature dependence analysis and constitutive modeling of the DSA-induced deformation twinning, which is a new plastic deformation mechanism discovered in several low-stacking-fault-energy metallic materials. Two types of deformation twinning, namely primary deformation twinning and DSA-induced deformation twinning, were noticed during the plastic deformation of the commercially pure titanium (CP–Ti). The strain, temperature, and strain rate ranges of the DSA-induced deformation twinning, as well as its rate-temperature coupling dependence, were systematically analyzed. The DSA-induced deformation twinning becomes more pronounced with the increasing strain rate and thereby plays a more significant role in enhancing the strain hardening rate than the primary deformation twinning. According to the dynamic Hall-Petch effect of the deformation twinning, a thermo-viscoplastic constitutive model based on the microstructural evolution and the thermal activation theory was developed. The volume fraction of the deformation twins during plastic deformation was expressed as a function of strain, temperature, and strain rate. The developed model was shown to be able to describe the S-shaped true stress vs. true strain curves over the wide ranges of temperature (77–998 K) and strain rate (0.001–8000/s). Finally, considering the interaction between the DSA and deformation twinning, the authors proposed the synergistic strengthening & toughening effect of DSA and deformation twinning, which was believed as a promising mechanism to achieve the simultaneous strengthening and toughing of the metallic materials.