Analysis of the deformation mechanisms in bulk ultrafine grained metallic materials

The upgraded Estrin-Tóth dislocation model has been suggested to describe deformation behavior of materials, subjected to severe plastic deformation, which in its turn is realized under high imposed pressure of several GPa. The model was applied to study high pressure torsion of Cu samples. The dislocation density evolution has been studied in the two phases: in the fragment/cell block boundaries and interiors. The evolution of concentration of vacancies, obtained during the deformation, and annihilation of dislocations during their non-conservative motion, generation of dislocations during multiple cross slip have been considered. Accounting of hydrostatic pressure was made in an explicit form on the basis of the presumption about limitation of the lattice diffusion, controlled by pressure. As a result the causes of achieving high values of flow stress, yield stress, dislocation density, vacancy concentration have been explained.