Low-Cycle Fatigue of Three Irradiated and Unirradiated Vanstar Alloys

Abstract

Results are reported for strain-controlled low-cycle fatigue measurements on Vanstar-7, 8, and 9 in both the irradiated and unirradiated conditions, conducted at 400°C. Specimens were irradiated in the experimental breeder reactor II (EBR-II) to fluences of 0.18 to 6.37 × 1025 neutrons (n)/m2 (E > 0.1 MeV) at 410 to 450°C. The results indicate that neutron irradiation had little or no effect on the fatigue life of any of the alloys. Comparison with data for Types 304 and 316 austenitic stainless steels tested at 400°C shows that on the basis of strain range the irradiated Vanstar alloys are inferior or equivalent to the stainless steels below 10 000 cycles-to-failure but become superior above that point. Proportional limit and yield-strength information have been extracted from the fatigue data, where possible. These data indicate that radiation hardening occurs rapidly at low neutron fluences and that strengthening saturates or increases very slowly above a fluence of approximately 1 × 1025 n/m2.