Irradiation creep by stress-induced preferential attraction due to anisotropic diffusion (SIPA-AD)

Abstract

An accepted mechanism for radiation creep is the dislocation climb enhancement via stress-induced preferential attraction (SIPA) of point defects. This attraction depends on the dislocation orientation with respect to the stress. It has been proposed as being induced by the second-order elastic interaction energy between the dislocation and the point defect, which is modelled as a polarizable inhomogeneity in a stress field (SIPA-I). An alternative mechanism is presented here: the stress-induced preferential attraction due to anisotropic diffusion (SIPA-AD). This is based on considering the point defect migration in an atomic lattice distorted by the dislocation and external stress fields; i.e. only the first-order size and shape interaction energy is considered but the discrete, anisotropic nature of the migration process is explicitly included. The dislocation sink strengths are calculated for different orientations and values of an external uniaxial stress and compared with the corresponding SIPA-I strengths for a characteristic fcc lattice. A simplified rate theory is used for modelling and comparing the irradiation creep predicted by SIPA-AD against the SIPA-I model. Larger creep rates and a different temperature dependence are found for SIPA-AD.