In-situ TEM study of the effect of pre-existing dislocation on loop evolution in 508-III steel during Fe+ irradiation

This study explores the evolution processes of initiation, migration, growth, annihilation, and aggregation for dislocation loops and dislocation complex formation in regions with and without pre-existing dislocations. In-situ TEM experimental observations are conducted for 508-III steel, commonly used as a pressure vessel steel in nuclear reactors, during 400 keV Fe+ irradiation at 573 K. Loop initiation is always observed, even following the formation of dislocation complex. The average size and number density of dislocation loops, in regions both with and without pre-existing dislocations, are obtained as a function of the irradiation dose. At the initial stage of irradiation, pre-existing dislocations significantly influence the evolution of dislocation loops. However, with an increase in the irradiation dose, this influence gradually weakens. The in-situ TEM experimental observations of microstructure evolutions in this study are of significant value for furthering our understanding of irradiation damage to 508-III steel.