Simulating the influence of radiation temperature variations on microstructural evolution

The influence of temperature variations on microstructural evolution in austenitic stainless steels is discussed in order to help interpret the response of materials in the HFIR-RB-13J temperature variation experiment. A kinetic microstructural evolution model developed for irradiated austenitic stainless steels was modified to provide a fully dynamic calculation of point defect and point defect cluster concentrations. Using the modified model, microstructural evolution was predicted for simulated HFIR-RB-13J temperature variation experiments and variations in material parameters were evaluated. The results indicate that repeated temperature excursion to 573 from 773 K always results in increased dislocation loop density and reduced cumulative defect flux within the calculated material parameter range, while excursions to 473 from 623 K may increase or decrease them depending on material parameters. The primary influence of temperature variation could be explained by accumulation and release of matrix defects at the temperatures of interest. The applicability of the current model must be further studied by careful investigation of the results from the HFIR-13J and related experiments.