Microstructural and textural evolution of pure titanium during differential speed rolling and subsequent annealing

The microstructural and textural evolution of pure titanium during differential speed rolling (DSR) at 500 °C and subsequent annealing were investigated using electron backscattered diffraction analysis. Twinning only occurs in the initial stage of DSR, and further deformation is dominated by dislocation slip. The as-rolled microstructure is characterized by large deformed grains, which form a major component of the material, and some dynamically recrystallized (DRXed) grains mainly existing in shear band regions. A dramatic change in the rolling texture, from the transverse direction (TD) split texture with basal poles largely tilted at ±40° to the single-peak basal texture, occurs during DSR. This change in texture is accelerated during the late stage of DSR and may be attributed to the gradual lattice rotation of deformed grains caused by enhanced basal slip activity. The basal texture changes back to the TD-split texture with basal poles tilted at ±25° after annealing due to consumption of deformed grains with basal orientations from DRXed grains with the TD-split texture. Subsequent extensive grain growth changes the orientation of the a-axis from parallel to the TD to parallel to the rolling direction, which is the result of the preferential grain growth in that direction.