Microstructural evolution in Fe-Cr-Ni alloy under variational temperature irradiation

It is expected that the temperature of structural materials in the future fusion devices changes frequently during irradiation. In order to understand the mechanisms of microstructural evolution under variational temperature irradiation, Fe-Cr-Ni austenitic alloys were irradiated with fission neutrons of JMTR and heavy ions at variational temperature. Most of the interstitial loops formed at low temperature disappear in the succeeding irradiation at high temperature. In the case of neutron irradiation, the formation of both interstitial loops and voids were suppressed in Fe-Cr-Ni alloy. Suppression of interstitial loop formation was also remarkable, but unexpectedly large void swelling was observed in Fe-Cr-Ni-Ti alloy. Numerical calculations using rate theory indicate that the radiation induced resolution of small vacancy clusters causes vacancy-rich condition temporarily under variational temperature irradiation. (author)