Irradiation hardening and embrittlement in high-Cr oxide dispersion strengthened steels

Abstract

The effects of neutron irradiation on the mechanical properties of high-Cr oxide dispersion strengthened (ODS) ferritic steels were observed. The materials used were produced by varying the Cr content from 14 to 22 wt% while maintaining the yittria contents within the range of 0.36–0.38 wt%. The ODS steels were irradiated in JMTR at 300, 420 and 550 °C to 5.56 × 10 20 n/cm 2 (>1 MeV). Charpy impact tests were performed between −150 °C and room temperature. The upper shelf energy (USE) of all ODS steel samples were reduced after irradiation. However, the reduction became smaller as the irradiation temperature increased. When the ODS steels were irradiated at 300 and 420 °C, the ductile-to-brittle transition temperature increased significantly. Tensile tests of the ODS steels irradiated at 300 °C were performed at room temperature with a strain rate of 6.7 × 10 −4 s −1. The yield stress and tensile strength of the irradiated ODS alloys increased significantly, and the level of irradiation hardening increased with the Cr content. Anisotropy was not observed in the yield stress and tensile strength but was observed in the elongation.