Irradiation-induced stress relaxation of Eurofer97 steel

The irradiation-induced stress relaxation behavior of Eurofer97 at 300 °C up to 3.4 dpa and under pre-stress loads typical for the ITER applications is investigated. The bolt specimens are pre-loaded from 30% to 90% of the yield strength. To verify the results obtained with the pre-stressed bolts, bent strips were investigated as well. The strips are bent into a pre-defined radius in order to achieve similar pre-stress levels. The irradiation-induced stress relaxation is found to be independent of the pre-stress level. 10–12% of the stress relaxation in Eurofer97 may be reached after a dose of 0.1 dpa, and after an irradiation dose of 2.7 dpa 42–47% of the original pre-stress is retained.