Effects of neutron irradiation on 12Cr–6Al-ODS steel with electron-beam weld line

Abstract

Oxide dispersion strengthened (ODS) steels have been developed as accident tolerant fuel cladding materials because of their excellent high temperature oxidation resistance as well as high temperature mechanical properties. 12Cr–6Al-ODS steel specimens with electron-beam (EB) weld line were irradiated with neutron in high flux isotope reactor (HFIR) at 300 °C to 2.6 dpa. Irradiation hardening was measured by Vickers hardness (HV) method. The irradiation resulted in a hardening of ∼95 HV in the base metal and ∼140 HV in EB weld line. The post-irradiation microstructures including the stability of the oxide nanoparticles was examined by transmission electron microscopy (TEM). The dispersion morphology of oxide particles in base metal was rather stable under present irradiation condition as no significant change was observed with respect to their average size and number density. As for the oxides in EB weld line, a similar trend with base metal was recognized. The 1/2 < 111 > and < 100> type dislocation loops formed in both base metal and EB weld line after neutron irradiation. The average size of dislocation loops was measured to be 7.6 ± 3.8 and 10.0 ± 3.8 nm in base metal and EB weld line, respectively. Meanwhile, the total number density was estimated to be (1.6 ± 1.0) × 1022 and (2.2 ± 0.5) × 1022 m−3 in base metal and EB weld line, respectively. Oxide/matrix interface may act as a trapping site for irradiation induced defects, leading to the smaller loop size and number density in base metal than in EB weld line. Dispersed barrier hardening (DBH) model indicated that the irradiation hardening could be attributed to the formation of dislocation loops.