Kinetic mechanism of the formation of fragmented dislocation structures upon large plastic deformations

The mechanism of formation of fragmented (banded, block) dislocation structures (FDSs) in crystals subjected to large plastic deformations are discussed. The theoretical analysis is based on the kinetic equations for the density of geometrically necessary dislocations (GNDs). The equations include the processes of multiplication, immobilization, annihilation, and diffusion of GNDs. The formation of an FDS is considered a synergetic process of self-organization of GNDs obeying the principle of similitude of dislocation structures at various degrees of plastic deformation. Conditions for the formation of the structures at hand have been determined, as well as their parameters and the dependence of these parameters on the degree of deformation. The theoretical results are compared with the available experimental data.