Abstract
There have been many previous studies on dislocation structures developed in copper single crystals during cyclic deformation. Formation and development of deformation bands have been reported in copper single crystals with the [111] multiple slip orientation. The study of deformation bands is important because they become crack initiation sites; however, their formation mechanism has not been well investigated. In this study, therefore, push-pull fatigue tests of the [111] copper single crystals were conducted under constant plastic shear strain amplitudes between 2.0 × 10−4 and 1.0 × 10−2 at room temperature. The deformation bands and dislocation structures in the fatigued specimens were observed by the electron-channeling contrast imaging technique of scanning electron microscopy and high-voltage scanning transmission electron microscopy. Bands of secondary slip (BSSs) and kink bands (KBs), which are parallel and perpendicular to the primary slip plane, respectively, were observed in cyclically softened specimens. Within the BSS and KB, cell bands with crystallographic misorientation were developed parallel to the {112} planes, which are perpendicular to the cross-slip plane and parallel to the primary slip direction. Cell boundaries in KBs consisted of three types of dislocations, including sessile dislocations.
