The paper deals with the application of Berg–Barrett X-ray topography to deformed copper single crystals. The imaged surfaces were sectioned from the deformed bulk crystals parallel to low-index planes.In stage I of the work-hardening curve, the braids of primary edge-dislocation dipoles, well known from electron transmission microscopy, have been observed over lengths of several tenths of a millimeter. Whereas in stage 1 the slip appears to be rather homogeneous and without strong interaction between primary and secondary slip systems, the transition region to stage 11 displays, as a characteristic feature, a systematic interaction of both types of slip systems, giving rise to layer-like dislocation structures about parallel to the primary slip plane. These layers, as in stage 11, are connected with a special type of lattice rotation. In stage II, dislocation walls or wall fragments perpendicular to the primary slip direction are observed. Generally, these walls are accompanied on either side by an extended region with an excess density of primary edge dislocation of one sign ("kink-walls"). As an example, the excess density at a flow stress τ ≈ 1–2 kg/mm2 is found to be of the order of 108/cm2.
Generation of Secondary Slip at Stage II in the Deformation of Copper Single Crystals