Deformation structure in stainless steels irradiated in a PWR

Surface steps and microstructure in stainless steels irradiated in a pressurized water reactor were examined after deformation up to 3% nominal plastic strain at 320degC. Deformation in the plastic region produced coarse steps. The width of the steps increased with dose, indicating that strain heterogeneity increases with dose. Transmission electron microscope observations revealed that coarse dislocation channeling on {111} planes along <110> direction corresponded to the surface steps and that fine channeling occurred between coarse slips. Grain boundary separation associated with ledge formation was evident at the intersections of coarse slips and grain boundaries whose plane was nearly normal to tensile axis. The results confirmed that coarse dislocation channeling produces a high level of stress at the intersection with grain boundaries, resulting in grain boundary separation. (author)