INSITU STUDY OF THE MIGRATION OF GRAIN-BOUNDARY FACETS IN AU BICRYSTALS UNDER HIGH DRIVING FORCES

A study is made of the migration of grain boundary facets possessing s imple intrinsic dislocation structures in gold by means of hot-stage i n-situ transmission electron microscopy making use of capillary-induce d high driving forces which occur during initial grain growth in bonde d thin-film bicrystals. In the case of low-angle tilt boundary facets the migration occurs by the nucleation of pairs of boundary steps and their subsequent lateral motion via glide processes of the component p rimary dislocations. These events can be video recorded and analysed o n a subsecond time scale. Experiments with high-angle near-SIGMA5 grai n boundaries indicate that the migration occurs by the shuffling of at oms directly across the interface. The secondary dislocations which ar e present move along with the boundary but are not involved in the pri mary migration mechanism. The measured boundary kinetics are discussed quantitatively on the basis of the proposed shuffling mechanism.