EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Understanding the effects of irradiation damage from fusion reactor environments on the properties of structural materials is crucial for safe and efficient reactor design. The study of FeCr binary alloys provides fundamental insights into irradiation damage and defect behaviour without the microstructural complexities of steels.

Previous studies of irradiated FeCr have largely focused on the structure of irradiation-induced defects, probed by transmission electron microscopy (TEM), as well as changes in mechanical properties. Key properties, such as irradiation-induced changes in thermal transport and lattice strain, are little explored along with the relationship between defect structures and material properties.

We have conducted a systematic study of Fe3Cr, Fe5Cr and Fe10Cr alloys implanted with 20 MeV Fe3+ ions to nominal doses of 0.01 dpa and 0.1 dpa at room temperature. Nanoindentation, transient grating spectroscopy (TGS) and X-ray micro-beam Laue diffraction were used to study the changes in hardness, thermal diffusivity and strain in the material as a function of damage and Cr content. Our results suggest that Cr leads to an increased retention of irradiation-induced defects, causing substantial changes in hardness and lattice strain. Thermal diffusivity was measured for the first time with TGS in irradiated FeCr and its degradation is found to be dominated by the presence of Cr while the effect of the defect population is small. We find significant lattice strains which cannot be fully account for by the visible defects observed in TEM, suggesting that TEM may not fully capture the irradiation-induced defect population.

The comparison of trends across different material properties reveals unique insights into the behaviour of defects and their effect on the FeCr material system. These results will be useful for understanding irradiation damage in more complex steels and demonstrate the potential of using TGS and X-ray based techniques for the characterisation of irradiated structural materials.