Grain size and temperature mediated twinning ability and strength-ductility correlation in pure titanium

The influence of grain size and temperature mediated twinning ability on mechanical properties of pure Ti is investigated in this study. A remarkable work-hardening ability was found in the uniaxial tensile stress-strain curve obtained at liquid nitrogen temperature, leading to a higher ultimate tensile stress and improved total ductility compared with the room temperature values. Evidence of microstructure and misorientation evolvement during tensile testing was provided to prove that twinning was prevalent in larger grains at lower temperature. The generation of twinning can provide additional boundary strengthening and work hardening capability by adjusting the parent grain orientation. The transition from traditional grain-boundary strengthening to dynamic twinning strengthening contributes to the outstanding strength-ductility combination, which follows a modified Hall-Petch relationship showing a strong synergistic effect of grain boundary and twinning.