Particle stability in model ODS steel irradiated up to 100 dpa at 600 °C: TEM and nano-indentation investigation

This paper is an experimental investigation of high temperature-dose stability of yttria particle dispersions in pure Fe matrix. Irradiation experiments were performed using single Fe and dual Fe and He ion beams, up to 100 dpa/360 appm He at 600 °C. Irradiation-induced evolutions are investigated by means of TEM observations, in combination with nano-indentation measurements. Particle stability at 600 °C is directly confirmed, up to 25 dpa/40 ppm He, while pronounced evolution of particle size distribution is evidenced at 80 dpa/360 ppm He. Diminution of particle density and particle coarsening is reflected in a significant evolution of the nano-indentation response. The change in the micro-mechanical evolution is ascribed to enhanced strain localization, associated with irradiation-induced particle size changes. Radiation-induced defect cluster and void formation are not detectable using TEM observations, in the whole investigated temperature/dose domain. Specific effect of implanted He is the augmentation of the micro-mechanical yields stress.