Effects of <I>In Situ</I> Irradiation by 20 MeV Protons on the Fatigue Properties of 316 Stainless Steel

Abstract

The effects of irradiation on the fatigue properties of stainless steel were studied under the condition of in situ irradiation or after irradiation using 20 MeV protons. Strain controlled fatigue tests using a resonant vibration of specimens at about 100 Hz with a total strain amplitude εt of (6∼12)×10−4 were made at 333 K on miniature specimens of solution treated SUS 316. The proton irradiation was made at about 333 K with irradiating current densities of 0.005–0.25 μA/cm2 (0.02–1×10−8 dpa/s). Changes in a vibrational period P and a drive force DF at constant εt were measured in situ during the test. Whereas the present damage rate was very low, the apparent effects of in situ irradiation on the fatigue properties were observed, e.g. the elongation of fatigue lives by about twice and the appearance of irradiation hardening for ∼1×10−8 dpa/s. The changes in fatigue properties observed after irradiation of ∼1×10−4 dpa were very similar to those obtained for in situ irradiation with ∼1×10−8 dpa/s. These results are discussed in detail.