The interaction energy between interstitial atoms and dislocations and its relevance to irradiation damage processes

To assess the suitability of alloy materials for the structural components of fast fission or fusion reactors, it is necessary to understand the various processes that influence the evolution of the microstructure of such materials when subjected to irradiation. In particular the vacancies and interstitials created during the irradiation will interact with existing dislocation lines and, under appropriate conditions can be lost at such sinks. To estimate the quantitative nature of such point defect loss it is necessary to calculate the point defect-dislocation interaction energies accurately. In this paper such calculations are described for both straight dislocations and dislocation loops in both a stress-free body and in a body subjected to an external uniaxial tensile stress. The relatively large distortion field associated with the interstitial compared to the vacancy ensures that only the dislocation-interstitial interactions need be considered. The stress-free interaction is dominated by the first order size effect and is considered to be the fundamental cause of such important phenomena as void swelling. On the other hand when a stress is present, important stress induced inhomogeneity interactions can prevail that will distinguish between dislocations of differing orientations relative to the applied stress. (author)