Uniaxial tensile deformation of single-crystalline and polycrystalline α-Ti models was numerically simulated with strain rates ranging from 10-4 to 10-1 [/s] using a crystal plasticity finite element method, and we investigated the relationship between the activities of the basal and prismatic <a> slip systems and the critical resolved shear stresses (CRSSs) depending on the strain rates. The simulation of single-crystalline model showed that CRSS of prismatic <a> slip system was easier to increase than that of basal slip system although CRSS of both slip systems increased with strain rates. The nature of strain rate dependency affected the deformation mechanism of polycrystalline model: the simulation of polycrystalline model showed that the activity of basal slip system increased locally with strain rates, instead of reducing that of prismatic <a> slip system. However, the local activation of basal slip system was inhibited when 1st pyramidal <a> slip system was activated. These results indicate that the local activation of basal slip system can occur by strain redistribution between preferred regions for basal and prismatic <a> slips with strain rates while activation of another slip system can inhibit that of the basal slip system.
