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a b s t r a c tThe present work investigates the irradiation hardening of Fe-based model ferritic alloys after Fe-ion irradiation experiments in order to deduce mechanistically based nominal hardness from the nanoindentation tests on the ion-irradiated surface. Ion-irradiation experiments were carried out at 290 • C with 6.4 MeV Fe 3+ ions. The constant stiffness measurement (CSM) was used to obtain the depthprofile of hardness. The results has been analyzed and discussed based on the Nix-Gao model and an extended film/substrate system hardness model. The depth-sensing nano-indentation techniques with CSM revealed that the hardness gradient of the unirradiated Fe-based model alloy can be explained through the indentation size effect (ISE). On the other hand, the gradient of ion-irradiated surface of these samples includes not only the ISE but also softer substrate effect (SSE). We propose a new approach to evaluate a nominal hardness, which may connect to the bulk hardness, from experimentally obtained nano-hardness depth profile data.

Tungsten materials are candidates for plasma-facing components for the International Thermonuclear Experimental Reactor and the DEMOnstration power plant because of their superior thermophysical properties. Because these materials are not common structural materials like steels, knowledge and strategies to improve the properties are still under development. These strategies discussed here, include new alloying approaches and microstructural stabilization by oxide dispersion strengthened as well as TiC stabilized tungsten based materials. The fracture behavior is improved by using tungsten laminated and tungsten wire reinforced materials. Material development is accompanied by neutron irradiation campaigns. Self-passivation, which is essential in case of loss-of-coolant accidents for plasma facing materials, can be achieved by certain amounts of chromium and titanium. Furthermore, modeling and computer simulation on the influence of alloying elements and heat loading and helium bombardment will be presented.