Effect of oxygen content on active deformation systems in pure titanium polycrystals

The Ti-0.1 wt% 0 and Ti-0.3 wt% 0 polycrystals were compressed along the extrusion direction and the incidence of different deformation modes were evaluated by electron backscattered diffraction (EBSD)-assisted slip trace analysis. It was found that a transition from single prismatic slip in Ti-0.10 to double prismatic slip or multiple slip in Ti-0.30 polycrystals dominated flow was observed. The reason for such transition was associated with the decreasing of CRSSpyramidal/CRSSprismatic ratio and the increasing of c/a ratio as the oxygen content increasing. Meanwhile, the deformation twins were less observed in Ti-0.30 than that in Ti-0.10 polycrystals, and all the characterized deformation twins were {10 (1) over bar2}((1) over bar 011). Interestingly, because the influence of the grain orientation and high local stress concentrations, {10 (1) over bar2}((1) over bar 011) twins with lower Schmid factor (SF) than that of prismatic slip were often activated in Ti-0.10 polycrystals. As the oxygen content increases, the interaction between the solute oxygen and the core of crew dislocation was enhanced, and the mobility of the dislocation becomes difficult. As a consequence, the compressive yield stress of Ti-0.30 was about 2.5 times that of Ti-0.10 polycrystals.