In situ observation of superdislocation motion in pre-strained Ni3Ge single crystals

Dislocation structures and their effect on the superdislocation motion in Ni3Ge single crystals have been studied by two-step deformation. In these tests either octahedral or cube slips were induced by prestraining. A difference in the induced dislocation structure is found to cause a notable change in the second deformation step depending on the combination of the stress axes. In order to understand the orientation sensitive hardening, in-situ deformation experiments have been made on the prestrained specimens in a high voltage electron microscope. Besides observation of the structural change due to dislocation motion, electron irradiation, which decorates antiphase boundary tubes, is utilized to trace the history of the rapid dislocation motion. Based on these observations, the origin of the anomalous strengthening in Ni3Ge is discussed with particular interest in the fine and non-planar dislocation structures induced by cross slips and dislocation-dislocation interactions.