Effects of Temperature and Strain Rate on the Low Cycle Fatigue Properties of Neutron Irradiated Stainless Steel DIN 1.4948

Low cycle fatigue (lcf specimens of stainless steel DIN 1.4948, which is similar to AISI Type 304, have been irradiated to a relatively low fluence level of maximally 5.10/sup 24/ n.m/sup -2/ (E > 0.1 MeV) at temperatures ranging from 330 to 923 K. Post-irradiation fatigue tests at the conventional strain rate (epsilon) of 3.10/sup -3/S/sup -1/, were performed at temperatures ranging from 298 to 1023K. Tests at low strain rates, ranging from 1.10/sup -6/ to 1.10/sup -3/s/sup -1/, were performed at 823 and 923 K. Irradiation hardening after the low temperature irradiations (623 K and below) caused no effect on the fatigue life. After irradiation at the higher temperatures the fatigue life was significantly reduced due to enhanced intergranular crack formation. This effect increased with increasing temperature and decreasing strain rate. The fatigue life reduction factor (N/sub f//sub unirr.//N/sub f//sub irr./) increased from a value of one at 723 K to three at 1023 K for tests with the conventional strain rate. The strain rate effect was strongest at 823 K. The post-irradiation fatigue life decreased from 2000 cycles at epsilon of 3.10/sup -3/s/sup -1/ to 90 cycles at the low strain rate of 2.10/sup -6/s/sup -1/ for testsmore » with 1.0 percent strain range at 823 K.« less