No abstract

No abstract

No abstract

The development and thorough characterization of DEMO relevant structural materials as well as their validation under fusion relevant conditions are the prerequisites for reliable design and safe and successful operation of the DEMO and belong to the key tasks within the European long term fusion R&D programme. The current work focuses on the Low Cycle Fatigue (LCF) behaviour of RAFM steels irradiated to a displacement damage doses up to 70 dpa at 330-337 °C in the experimental fast reactor Bor 60 within the ARBOR 2 irradiation programme. The influence of the neutron irradiation on the fatigue behaviour was determined for the as-received EUROFER97 (980 °C/0.5 h + 760 °C/1.5 h), pre-irradiation heat treated EUROFER97 HT (1040 °C/0.5 h + 760 °C/1.5 h) and pre-irradiation heat treated F82H-mod (1040 °C/38 min + 750 °C/2 h) steels. The strain controlled push-pull loading was performed with miniaturized cylindrical specimens at a constant temperature of 330 °C with different total strain ranges (Δε tot) between 0.8 and 1.1 % and at common strain rate of 3x10-3 s-1. The comparison with the corresponding results in the reference unirradiated state was performed for both the adequate total and inelastic strain amplitudes. The neutron irradiation induced hardening can affect differently the fatigue behaviour of the irradiated specimens. The reduction of the inelastic strain in the irradiated state compared to the reference unirradiated state for common total strain amplitudes can yield increase of fatigue lifetime. The increase of the stress for the adequate inelastic strain in contrast might accelerate the fatigue damage accumulation. Depending upon which of the two mentioned effects is dominant the neutron irradiation can either extend or reduce the fatigue lifetime compared to the reference unirradiated state. The experimental results on EUROFER97 and EUROFER97 HT support the above considerations. Most of the irradiated specimens show fatigue lifetimes which are comparable to the reference unirradiated state for adequate inelastic strains. In some cases, however, lifetime reduction is observable. F82H mod showed partly lifetime enhancement compared to the reference unirradiated state for adequate inelastic strains.

No abstract