A source model for work hardening of single crystals

Abstract

The sources, i.e. regions of glide band nucleation in the crystal, are characterized by a locally softened lattice as compared to regions with a perfect lattice. Hence, the depletion of the set of sources during work hardening suggests that the latter can be considered as gradual loss by the crystal of the softening pertaining to the source regions. This model is a realization of A. V. Stepanov's ideas who considered work hardening to be “... disappearance of shear nuclei capable of growth” [21]. It relates the macroscopic plasticity characteristics both with parameters of a non-deformed real crystal (i.e.N(τ)) and with properties of the dislocation ensemble and its internal stress field determiningh (τ, ζ). The model permits of different degrees of accuracy in the description of theτ-e curve, corresponding to a more or less complete account of the contributions due to individual glide bands and their interaction with band sources still unactivated. In its turn, the model can be naturally incorporated in a more general scheme taking into account the time dependence of work hardening as well [8]. Further development of the model would require calculation of dislocation appearance in the surface source regions of the crystals with an account of the lattice imperfection in those regions well before the nucleation of dislocation loops.