The Stability of 9Cr-ODS Oxide Particles Under Heavy-Ion Irradiation

An oxide-dispersion-strengthened (ODS) martensitic steel 9Cr-ODS was irradiated with 5-MeV Ni ions at 500 (degree) C at a dose rate of 1.4 * 10^-3 dpa/s to doses of 5, 50, and 150 dpa. The ODS steel has been designed for use in highertemperature energy systems. However, the radiation effects are not fully characterized, particularly to high doses. Dense dislocations, precipitates, and yttrium-titanium oxide particles dominated the microstructure of 9Cr-ODS for both the unirradiated and irradiated cases with no dislocation loops observed. No voids were detected for doses up to 150 dpa. The average size of the oxide particles, whose size is approximately described by a lognormal distribution, slightly decreased with dose from ~12 nm for the unirradiated case to ~9 nm at 150 dpa. The decrease in size follows a square root of dose dependency, indicating the effect is radiation induced. The decrease in size is not expected to have a detrimental effect on high-temperature strength, even to extremely high dose.