A modeling of radiation induced microstructural evolution under applied stress in austenitic alloys

Effects of applied stress on interstitial type Frank loop evolution at early stages of irradiation were investigated by both numerical calculation and irradiation experiments. In the experimental part of this work, microstructural inspection has been made by transmission electron microscopy with a special emphasis on Frank loops and perfect loops on every {111} plane. The results of the TEM observation revealed that Frank loop concentration on a {111} plane increased as the resolved normal stress to a {111} plane increased and that small perfect loops were more likely produced on {111} planes where larger resolved shear stress was applied. The model of a stress effect on Frank loop unfolding was provided, which is triggered by nucleation of a Shockley partial dislocation loop in a Frank loop, was proposed. The results of the numerical calculation was successful to predict the strong dependence of Frank loop concentration on the resolved normal stress to {111} plane, which was the characteristic feature seen in the irradiation experiments.