Structure of titanium subjected to dynamic channel-angular pressing in copper shells

It has been established using metallography and electron microscopy that the dynamic channel-angular pressing of titanium in cylindrical copper shells of a sufficient thickness removes the effects of localized deformation in the form of cracks and adiabatic shear bands, which were observed upon deformation without shells. This mode of deformation is effected via the formation of numerous twins; as a result, the initial grains become divided into small regions. Together with twins of ordinary morphology in the form of plates, there are observed wavy bent “noncrystallographic” twins, whose appearance is caused by the rotational deformation modes. Twins in the form of rods have been revealed, which sometimes are grouped into lamellar packets arranged perpendicularly to the longitudinal axis of the sample. The formation of numerous twins in titanium during dynamic channel-angular pressing leads to an increase in the microhardness by 15–35%. Twinning can be used to increase the strength characteristics of titanium, additionally to the creation of nanocrystalline and submicrocrystalline structures.