Nanocrystalline copper films were prepared by sputtering and then in situ straining experiments were performed using a trans- mission electron microscope. Macroscopically, these copper films exhibited very low ductili...Nanocrystalline copper films were prepared by sputtering and then in situ straining experiments were performed using a trans- mission electron microscope. Macroscopically, these copper films exhibited very low ductility (<l%). Dislocation activity was limited in regions far from propagating cracks. Near stable growing cracks, considerable local plasticity was observed. The evidence of slip ac- tivity both within grain interiors and in grain boundaries was also observed. Although some dislocation; moved very fast, others showed rates much lower than those typically measured for bulk copper. Fracture was intergranular, but not brittle. It occurred by linking of microcracks. Microcracks formed within a micrometer or so ahead of the main crack tip, usually within a grain boundary. Linking then took place by the easiest available path.展开更多
文摘Nanocrystalline copper films were prepared by sputtering and then in situ straining experiments were performed using a trans- mission electron microscope. Macroscopically, these copper films exhibited very low ductility (<l%). Dislocation activity was limited in regions far from propagating cracks. Near stable growing cracks, considerable local plasticity was observed. The evidence of slip ac- tivity both within grain interiors and in grain boundaries was also observed. Although some dislocation; moved very fast, others showed rates much lower than those typically measured for bulk copper. Fracture was intergranular, but not brittle. It occurred by linking of microcracks. Microcracks formed within a micrometer or so ahead of the main crack tip, usually within a grain boundary. Linking then took place by the easiest available path.
