Radiation tolerance of alumina scale formed on FeCrAl ODS ferritic alloy

Alumina-forming FeCrAl oxide dispersion strengthened (ODS) ferritic alloys are considered as promising structure materials for the next-generation nuclear reactors. Current work is aimed at investigating Fe ion irradiation effect on the alumina scale formed on FeCrAl ODS ferritic alloy. A single alpha-alumina layer with a thickness of about 0.7 µm was formed on the surface of the alloy by a pre-oxidation process at 1000 °C with 9 h. The pre-oxidized specimen was subsequently irradiated using 6.4 MeV Fe3+ ion beam to 2 dpa at 500 °C. Nanoindentation testing demonstrated that the hardness of the alumina scale decreased after the Fe ion irradiation. Corresponding microstructure characterization was carried out by using electron backscatter diffraction (EBSD) and scanning transmission electron microscopy (STEM). Alumina grain growth and softening in accordance with the Hall-Petch relationship are responsible for the hardness decrease by the Fe ion implantation. Irradiation-induced dissolution of Y-Zr oxide particles in alumina grains as well as the irradiation-induced segregation of reactive elements along the alumina grain boundaries were observed.