It was recalled that the effects of cyclic temperature changes upon the radiation-induced microstructural evolution of Fe-Cr-Ni alloys were extensive and complicated. In order to clarify them, the accumulation of defects under varying-temperature irradiation were calculated on the basis of the rate theory for defect clustering. The results indicated that the microstructural evolution under varying-temperature irradiation was such that vacancy-predominant conditions appeared after changing the temperature from low to high. This was attributed to the decomposition of small vacancy clusters, which had formed during the low-temperature irradiation, by reaction with interstitials that were produced by irradiation at the higher temperature. Interstitial clusters therefore shrank, while vacancy clusters grew by absorbing the excess vacancies. In the case of temperature changes from high to low, an interstitial-predominant condition was maintained throughout the entire irradiation period. Interstitial clusters therefore grew while vacancy clusters shrank. During temperature-cycling irradiation, large interstitial and vacancy clusters were difficult to form because these clusters grew and shrank repeatedly during the periodic temperature changes.

Defect Formation Processes in Fe-Cr-Ni Alloys by Neutron Irradiation under Thermal Cycles Q.Xu, N.Yoshida, T.Yoshiie: Materials Transactions, 1997, 38[10], 836-41