Local slip activities in polycrystalline α-Ti depending on textures and strain rates

It is possible that strain localization in polycrystalline α-Ti leads to the fracture, and it is crucial to evaluate the local slip activities for individual slip systems depending on their textures and loading conditions. In this study, the effects of textures and strain rates on local slip activities were investigated using the crystal plasticity finite element method. For the analysis, microstructural models of α-Ti with the following three textures were employed: aggregates of (0001) axes are (i) splitting in rolling direction (RD-split texture), (ii) splitting in transverse direction (TD-split texture), and (iii) aligned in normal direction (basal texture). For each texture model, two variations in the crystal orientation distributions were considered, namely, small and large scatterings of crystal orientations in the (0001) axes by normal random numbers. The differences in the strain rate sensitivities of the critical resolved shear stresses (CRSSs) among slip systems were also considered. Tensile loading was applied by a forced displacement in the RD with two strain rate conditions of 1.0 × 10⁻⁴ s⁻¹ and 1.0 × 10⁻¹ s⁻¹. Local non-prismatic slips were easier to operate in the models with basal and RD-split textures than with the TD-split texture. The slip strains for non-prismatic slip systems were higher at higher strain rates, while activities in the prismatic slips decreased with an increase in strain rates. The mechanism of the exchange of slip system activities can be explained by strain redistribution between hard and soft regions and changes in CRSS as a function of strain rates.