Currently envisioned fusion reactors require materials capable of operating in a high-energy irradiation environment and at elevated temperatures. In this study, two nonstandard miniature bending fatigue specimens have been developed for scoping candidate first wall materials for fusion reactors. The first specimen is the “rectangular specimen,” with a gauge length of 6.35 mm and dimensions of 30.16 by 4.76 by 0.76 mm. The second specimen, referred to as the “miniature-disk specimen,” is cut from a 3-mm transmission electron microscope disk with a gauge section of length 1.5 mm.

Test results for unirradiated, annealed Type 316 stainless steel at 25, 550, and 650°C are presented. The results are presented as a plot of total strain range as a function of cycles to failure. Comparison of the results at room and elevated temperatures for both specimens with results obtained using the subsize axial specimen developed at Oak Ridge National Laboratory are given. The miniature specimen results show the same dependence of strain range on cycles to failure as the standard axial specimen results. Results were analyzed using a power law type equation relating the total strain range to cycles to failure. The elevated temperature results for the rectangular specimen fell below the room temperature data. A similar temperature dependence was not evident for the miniature disk specimen results.