Localization of plastic deformation and mechanical twinning in dynamical channel angular pressing

We have performed numerical simulations for the early stages (till several tens of microseconds) of dynamical channel angular pressing (DCAP). New dislocation and twinning models have been used for description of the kinetics and dynamics of defect structures; these models are described in the paper. In DCAP of copper with the initial sample velocities ranging from 100 m/s to 250 m/s we have found that the shock wave propagation leads to appearance of microscopic shear bands, its growth and intersections. We suppose that it is the main mechanism of the nanocrystalline grain formation. Twinning takes place in DCAP and the volume fraction of twins can go up to 0.5. It can be supposed that the shear bands and twins formation at the early stages of DCAP leads to some special features of the microstructure, which differs these structures from the structures obtained after quasi-static ECAP processes.