Evaluation of thermal fatigue damage for high-strength materials with neutron irradiation

Abstract

1. Using the example of an irradiated, dispersion-hardened, chromium-nickel steel it has been shown that it is possible to compute its long-term thermocyclic strength on the basis of strain criteria for thermal fatigue failure using temperature-time and dose dependence for mechanical properties and structural parameters. 2. Relationships have been obtained for determining the temperature—time dependence of strength and ductility for high-strength materials of different structural classes with irradiation by fast neutrons up to extra large doses. 3. It has been shown that with high-temperature neutron irradiation of high-strength materials, processes which develop are radiation strengthening, annealing, and embrittlement accompanied by thermal strengthening (weakening). These processes, and also the original mechanical condition of the materials (brittle, semibrittle, and ductile), make a fundamental contribution to changes in long-term thermocyclic strength under reactor irradiation. 4. According to these studies, the reduction in long-term thermocyclic strength of high-strength materials with irradiation by a neutron flux of ∼ 1023 neutrons/cm2 may reach a factor of 2–10.