Substructure of Persistent Slip Bands in Cyclically Deformed Copper

Abstract
The dislocation distribution in the surface layer of cyclically deformed specimens of polycrystalline copper is studied by means of transmission electron microscopy of thin foils, both parallel and nonparallel to the surface. The distribution within the surface layer and near the persistent slip bands is found to differ considerably from that inside the specimens. The persistent slip bands consist of zones of alternately high and low dislocation density. The zones of high density link together at a particular depth below the surface. The zones of low density are assumed to serve as “channels” in which the motion of dislocations emitted from Frank‐Read sources is relatively free. The escape of these dislocations from the free surface results in surface extrusions.