Microstructure development during annealing in electron-irradiated 316L model alloy

Abstract

When the severe accident or some crucial troubles happen in nuclear power plants, the stop of coolant system and the increase in temperature to far exceeding from the normal operating condition could be predicted. The sudden increase in temperature would change microstructure of structural materials. In order to investigate the influence of annealing on microstructure development, in-situ electron irradiation experiment was carried out in 316L model alloy.Electron irradiation at 288 °C resulted in the formation of black dots, Flank loops and cavities in 316L model alloy. Black dots and Frank loops formed in the early stage of electron-irradiation and transferred to Flank loops and perfect loops, respectively. Annealing experiment at 500 °C for 120 min indicated that the number density and the mean size of Frank loops decreased after annealing. In addition, the mean size of cavities decreased, while the number density seemed not to be changed after annealing. Comparing the size distribution change before and after annealing experiment, it is suggested that Frank loops could be shrunk as a result of absorbing vacancies released from cavities during annealing.