Effects of strain rate on the formation and the tensile behaviors of multimodal grain structure titanium

In the present study, the effects of rolling strain rate on the microstructure evolutions and tensile properties of multimodal grain structure titanium prepared by cryorolling upon annealing has been investigated. As the strain rate increases, the dislocation density increases and the dynamic recovery is effectively suppressed. The recrystallization nucleation gradually increases during subsequent annealing. At high strain rate of 4.67 s(-1), a multimodal grain structure has been formed after employing a short-duration annealing on this cryorolled-Ti. This multimodal grain structure Ti exhibits combination of high strength and ductility. The high strength can be attributed to the nanoscale and ultrafine grains, and the enhanced ductility is mainly results from the improved strain hardening capability which attributed to the accommodation deformation mechanism between fine grains and coarse grains. These results demonstrate that tailoring the microstructure after annealing can be accomplished effectively by controlling the strain rate during cryorolling, which offer a processing strategy towards high strength and large ductility materials.