A dislocation dynamics analysis of the critical cross-slip annihilation distance and the cyclic saturation stress in fcc single crystals at different temperatures

Abstract

Cross-slip is treated as a deterministic, mechanically activated process governed by the applied stress, by the interaction force between approaching screw dislocations of the opposite sign and by the line tension related to the persistent slip band channel width. The dislocations are modeled as moving polygons. In the evaluation of the critical cross-slip annihilation distance and the saturation stress in cycling, we accept two assumptions inspired by Brown [Brown L. Philos Mag A 2002;82:1691]: (i) the critical parameter associated with cross-slip is the spreading of the dislocation loop on the cross-slip plane, not the critical formation of a constriction in an extended screw dislocation core. (ii) The saturation stress in cycling is controlled by the stress required to separate two screw dislocations of opposite signs which are just on the point of mutual annihilation by cross-slip. The proposed model predicts the critical annihilation distance and the cyclic saturation stress in agreement with the available experimental data for Cu, Ni and Ag single crystals.