The Processing and Bulk Properties of New Low-Activation High-Entropy Alloys

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Moving towards net-zero electricity production is critical for the UK's energy security and to reduce the impact of climate change. Nuclear fusion power is a prime candidate for long-term production of green electricity in the future. A number of existing metallic alloys have been proposed for use inside future fusion reactors, including in the plasma-facing components that experience the most challenging conditions. However, there remains a real possibility that these alloys are not suitable for use in such environments, since they have not been tested under the extreme conditions they will face (i.e., a high flux of fast neutrons and temperatures above 500C). Hence, there is a strong argument that new fusion-focussed alloys be designed and investigated to maximise our chances of a successful outcome.High-entropy alloys (HEAs) are a relatively new class of alloys that have generated a lot of interest in the materials science community over recent years. Instead of being based around one principal alloying element (e.g., Fe in steels), they comprise multiple elements in high concentrations. This design philosophy has opened up a huge range of alloy compositions that have not been explored before. Some work has been started on designing low-activation HEAs for fusion, i.e., alloys are less likely to become radioactive for a long period of time following exposure to fusion reactor conditions (and hence won't have to be deposed of as long-life radioactive waste).This project will 'scale-up' work on new low-activation HEA compositions that have already shown some promise, with particular focus on the VCrMnFeAlx suite of alloys (where x varies between 0 and 1). These alloys have been shown to exhibit good thermal stability, and some also exhibit some interesting microstructures that could lead to high-temperature strength. However, to date these compositions have only been assessed using very small quantities of material, so their bulk mechanical properties (e.g., stress-strain curves, high-temperature properties) have not been measured. Neither have their responses to bulk thermomechanical treatments that might be used during their large-scale manufacture. Hence, this project will use larger castings (on the scale of a few kgs) to assess such properties. Advanced high-resolution characterisation techniques will be used alongside conventional mechanical testing. All the results that are produced from these tests will be novel, since they have not been measured before for these alloys. Importantly, the results should indicate whether these materials are likely to be suitable for use in future fusion reactors.