Undoped or Zn-doped single crystals were deformed by compression in a single-slip orientation. Various strain rates and temperatures were used to deform the samples into stage III; the first recovery stage. Transmission electron microscopy was used to characterize the evolution of the dislocation structure during various stages of deformation, such as the easy-glide region (stage-I), the first work-hardening region (stage-II) and the first recovery region (stage-III). Stage-I of plastic deformation was characterized by dislocations on the primary slip system. Mainly edge dislocations and edge dipoles were observed, and were thought to result most probably from the cross-slip of screw dislocations. The dislocation structure in stage-II deformation consisted mainly of rectangular networks that extended parallel to the primary glide plane. The dislocation density increased further in stage III. A cell structure was observed which consisted of dense dislocation networks that surrounded regions which were almost free of dislocations. A detailed contrast analysis of the various dislocation types indicated that recovery was governed by climb processes.
M.Luysberg, D.Gerthsen: Philosophical Magazine A, 1997, 76, 45-62