High temperature irradiation effects in selected Generation IV structural alloys

In the Generation IV Materials Program cross-cutting task, irradiation and testing were carried out to address the issue of high temperature irradiation effects with selected current and potential candidate metallic alloys. The materials tested were (1) a high-nickel iron-base alloy (Alloy 800H); (2) a nickel-base alloy (Alloy 617); (3) two advanced nano-structured ferritic alloys (designated 14YWT and 14WT); and (4) a commercial ferritic–martensitic steel (annealed 9Cr–1MoV). Small tensile specimens were irradiated in rabbit capsules in the High-Flux Isotope Reactor at temperatures from about 550 to 700 °C and to irradiation doses in the range 1.2–1.6 dpa. The Alloy 800H and Alloy 617 exhibited significant hardening after irradiation at 580 °C; some hardening occurred at 660 °C as well, but the 800H showed extremely low tensile elongations when tested at 700 °C. Notably, the grain boundary engineered 800H exhibited even greater hardening at 580 °C and retained a high amount of ductility. Irradiation effects on the two nano-structured ferritic alloys and the annealed 9Cr–1MoV were relatively slight at this low dose.