Stability of oxide particles under electron irradiation in a 9Cr ODS steel at 400 °C

Oxide dispersion strengthened steel is one of the candidate materials as fuel cladding in generation IV system and fusion blanket material because of its superior high temperature mechanical properties. The instability of the nanometer-scale oxide particles was reported recently. The aim of this work is to clarify the detailed mechanism under electron irradiations. Simultaneous in-situ observations combined with focused beam electron irradiation were performed to observe the microstructural evolutions at 400 degrees C. Various phenomena, such as size change of the oxide particles and void formation were observed. The nanoparticles became smaller monotonically. Electron beam intensity was found to have a significant impact on the instability of the nanoparticles. The size change of the particles became faster under more intense beam or under greater gradient of electron intensity. The phenomena were interpreted based on the model which includes irradiation-induced vacancies in Fe-9Cr matrix and their diffusion according to the beam intensity profile which according to the beam intensity profile which correlates to the distribution of point defects. It was successfully deduced that the effect of vacancy assisted solute atom diffusion was to aid in the dissolving of the constituent atoms of the nanoparticles in the matrix. (C) 2014 Elsevier B.V. All rights reserved.