Microstructure and microtexture of highly cold-rolled commercially pure titanium

The microstructure and texture evolution of a commercially pure titanium sheet during cold-rolling is investigated in detail by X-ray diffraction and by orientation imaging in the FEG-SEM and in the TEM. The experimental data are compared with simulation results obtained by a viscoplastic self-consistent model. The aim of this work is to provide with a detailed description of the fine scale deformation structures obtained after 80% cold-rolling and to identify the mechanisms by which these structures form. Such a detailed investigation is nowadays possible thanks to high spatial resolution orientation imaging techniques. This work highlights the important role of mechanical twinning as one of the grain fragmentation mechanisms. The microstructure obtained after 80% thickness reduction can be separated into two distinct parts: 85 vol.% of the material is fine-subdivided with highly misoriented sub-micron features and the others 15 vol.% consist in lamellar structures formed in grains initially oriented in a particular region of orientation space, which have not undergone twinning. The influence of these structures on recrystallization mechanisms are also discussed.