Radiation-induced creep and swelling is formulated in terms of the segregation of vacancies and interstitials to the microstructural sinks, such as voids, dislocations, and dislocation loops, in order to provide the physical basis for the effect of stress on swelling, radiation-induced creep, and the interrelationship between swelling and irradiation creep.
It is first shown that the segregation is caused by the interaction between the point defects and the sinks and that the size interaction as well as the inhomogeneity interaction have to be considered. The latter interaction depends both on the external and the internal stresses. The segregation is then expressed in terms of bias factors for each sink type, and these factors are given for voids, small dislocation loops, and edge dislocation multipoles.
The bias factors for voids are shown to depend on the hydrostatic stress leading to a stress-dependent incubation time for void nucleation as well as a stress-dependent swelling rate.
The bias factors for dislocation loops depend on the deviatoric stress. Thus, the loop growth rate becomes orientation-dependent in a stress field, which gives rise to irradiation creep.
The comparison between the bias factors of voids and dislocation multipoles reveals that void nucleation is suppressed in cold-worked materials until sufficient recovery has occurred.
By including the bias factors for voids, dislocations, and dislocation loops into the models for swelling and irradiation creep, a constitutive law for radiation-induced deformation is obtained which includes the rates for stress-free swelling, stress-induced swelling, swelling-independent and swelling-dependent irradiation creep.