Dislocation motion and formation of dislocation structures during in situ deformation in a high voltage electron microscope

Abstract

Complex dislocation structures develop during in situ deformation of MgO single crystals in a high voltage electron microscope. In ionic crystals, slip usually starts at a few widely separated places. The slip bands broaden by cross-slip, which also controls the dislocation multiplication. Later on, oblique slip systems are activated. A great amount of dislocation debris is produced in the course of deformation. Most probably, the debris is responsible for a great part of the work hardening. Many details of the dislocation arrangement correspond to low energy dislocation structures. It is argued, however, that the deformation process is governed by a principle which keeps the flow stress as low as possible.