Features of slip-band formation during the plastic straining of layered crystals

The effects of the narrowing and branching of screw slip bands during the plastic straining of nonuniformly doped or nonuniformly irradiated (layered) crystals are discussed theoretically on the basis of the equations of dislocation kinetics. Band formation is treated as a process involving the self-organization of dislocations in a dislocation ensemble at the mesoscopic level. The distributions of the densities of mobile and immobile dislocations, as well as of the local plastic strain rate, in a slip band propagating in a layered crystal are obtained. It is found that the narrowing of bands is due to the lower rate of broadening of the bands in stiff layers than in soft layers, which have not been hardened by doping or irradiation, and that branching is due the low local strain rate in stiff layers compared with the strain rate per slip band assigned by the straining machine. In the latter case the nucleation of new bands or the branching of existing bands is required to restore the balance between these rates. Fiz. Tverd. Tela (St. Petersburg) 41, 252–258 (February 1999)