Dislocation-obstacle interactions at atomic level in irradiated metals

Nano-scale defect clusters, such as voids, dislocation loops, stacking-fault tetrahedra and irradiation-induced precipitates, are produced in metals by irradiation with high-energy atomic particles. They are obstacles to dislocation glide and can give rise to substantial changes in the yield and flow stresses and ductility. Atomic-scale computer simulation is able to provide detail of how these effects are influenced by obstacle structure, applied stress, strain rate and temperature. Some recent results from modelling dislocations interacting with obstacles are described. Emphasis is placed on dislocation interaction with voids, copper precipitates and dislocation loops in the BCC metal iron and stacking fault tetrahedra in FCC copper. In the latter case, the importance of surfaces in reactions in TEM foils is highlighted. It is shown that while some atomic processes can be represented adequately by the continuum theory of crystal defects, others cannot.