Observation of Dislocation Motion in Al Single-Crystal Films

Epitaxial Al films were evaporated onto polished surfaces of KCl substrates close to the orientation (123). They were single-crystal films with the substrate orientation and contained a few small twin-oriented inclusions. Portions of the films were mounted on an electron microscope straining stage and plastically deformed in uniaxial tension. They could be homogeneously strained by at least 1% before a crack develops. Dislocation motion was observed while the films were strained. In areas of homogeneous plastic flow, short dislocation lines extending from top to bottom surface of the film moved sideways on their {111} glide planes. They left slip traces on the surface which could be evaluated by diffraction contrast methods. A strong tendency for multiple slip was observed which depended on the relationships between Burgers vectors, film plane, and direction of applied stress.