TEM investigation on irradiation stability of oxide nano particles in model ODS alloy Fe-14Cr-0.2Ti-0.3Y2O3

Oxide Dispersion Strengthened steels (ODS) are considered as candidate structural materials of advanced fusion and fission reactors. As the reactor structural materials are exposed to high neutron fluence, study of irradiation stability of these particles is of crucial importance. In order to study irradiation stability, a model ODS alloy of composition Fe-14Cr-0.2Ti-0.3Y2O3 was taken for present study. The alloy was irradiated using 5 MeV Ni2+ ion beam to a dose of 150 dpa at 600℃ and 700 ℃ at JANNUS irradiation facility. A drastic reduction in particle size along with an increase in particle density was seen in the Fe-14Cr-0.2Ti-0.3Y2O3 sample irradiated upto 40 dpa and 700℃ as compared to 600℃. The average size came down from 10 nm (unirradiated alloy) to 1 nm size. The HRTEM investigation reveals that most of the oxide particles are Y2TiO5 and upon irradiation, the particle size becomes so small that difficult to confirm crystal structure and composition. The results will be discussed based on the irradiation conditions. (author)