TEW004 - Nanostructured refractory high entropy alloys for fusion power

Fusion power plants have the potential to offer a low carbon alternative to fossil fuel, providing a more sustainable way to generate electricity. However, materials within a fusion power plant will experience incredibly harsh environments, with high neutron fluxes, high temperatures, corrosion and plasma erosion. Furthermore, to minimise the environmental impact of fusion power the materials used must not produce long lived radioactive waste. These requirements push the limits of conventional materials and prove challenging to test, as few environments can accurately reflect the environment and levels of neutron irradiation that will be experienced in a commercial fusion power plant. Nevertheless, for fusion power to be realised materials capable of maintaining their desired properties, such as strength or thermal conductivity, are needed.

Refractory high entropy alloys are being considered as novel fusion materials, due to the high melting temperatures of their constituent elements, and promising irradiation damage resistance and recovery. High entropy alloy design methodologies focus on multi-principle element compositions offering the potential to find new alloys with advantageous combinations of properties. Additionally, has been proposed that the variations in atomic size within high entropy alloys could be beneficial for aiding recombination of vacancies and interstitial atoms following irradiation damage. The effects of irradiation damage can also be controlled by adding a fine dispersion of secondary phases to act as sinks. This project will therefore explore multiphase refractory high entropy alloys, comprised of elements that avoid long lived radioactive waste.

This project will produce systematic series of novel alloys, characterise the microstructures that form, determine key properties and explore their performance under irradiation. The compositional dependence of the phases present, the upper temperature at which the multiphase microstructure is stable and how it evolves with extended thermal exposure will be assessed with a variety of techniques such as TEM, XRD, DSC and SEM EDX, to determine the upper operational temperatures for these alloys, driving factors for coarsening and how compositional modification can improve their performance. Mechanical and thermal properties will be investigated and promising candidate alloys irradiated to ascertain whether they offer promising irradiation performance.