Irradiation-induced structural changes in martensitic steel T91

The microstructure of T91 (9Cr1Mo) martensitic steels have been investigated with SANS and ASAXS techniques after irradiation in SINQ Target-3 with protons and neutrons. The SANS investigations cover specimens irradiated to doses between 3.9 and 9.8 dpa at temperatures ⩽200 °C. The SANS intensities of the irradiated specimens show strong irradiation effects at Q > 0.7 nm−1. The differences between the different irradiation states are weak. From the magnetic scattering contribution the size distributions of the irradiation induced defects were calculated. All size distributions were rather narrow with maxima at a diameter of about 0.8 nm. The ASAXS measurements were performed on reference and two samples irradiated to 9.1 and 9.7 dpa at 150 and 300 °C, respectively. The variation of the X-ray energy close to the Cr–K-absorption edge results in a contrast variation and shows information about chromium-containing inhomogeneities. At Q > 0.7 nm no irradiation-induced chromium effect could be detected. It indicates that the irradiation defects detected by SANS do not contain chromium. The chromium-containing inhomogeneities induced by irradiation are larger than the defects detected by SANS.