Primary and secondary dislocation dipole heights in cyclically deformed copper single crystals

Copper single crystals were cyclically deformed in single slip to pre-saturation at ambient temperature. The microstructure consisted of dense dipole bundles separated by channels with low dislocation densities. The dipole height in the presaturation microstructure is approximately independent of location, being equal in the dipole bundles (or veins) as within the channels, for both primary and secondary dipoles. The maximum dipole heights suggest strengths that are about a factor of two higher than the flow stress. The above observations and the consideration of thermal activation to assist the separation of dipoles under stress suggest a homogenous stress distribution without internal stresses, although other interpretations are expressed in the literature.