Conclusion

Abstract

Dislocation motion is quite a complex process spanning several orders of magnitude in length scales. The motion is realized by breaking and re-establishing bonds on the atomic level. These problems are tackled by molecular dynamics simulations using semi-heuristic methods. Ab initio calculations are still rare and, for more complex problems, they suffer from the still low number of atoms involved. There is still poor microscopic experimental verification of these dynamic processes. The static core configurations of dislocations are studied by high-resolution electron microscopy. The spatial resolution of the latter techniques has drastically improved by the new aberration-corrected microscopes. However, the informative value of the micrographs is limited by the geometrical requirements to the specimens. Simple interpretations are possible only for edge dislocations arranged end-on in the specimen. Up to now, there are no TEM in situ loading studies under high-resolution conditions revealing changes of the core structure of relatively compact cores under load. This is due partly to experimental difficulties and partly to surface effects from the low specimen thicknesses, which influence the processes to be studied. Thus, in understanding the atomic processes of dislocation motion, there are still some challenges to be respected.