Understanding how irradiation damage from neutrons affects the mechanical properties of structural materials is a key step towards realising nuclear fusion as a sustainable power source. However working on irradiated materials is costly, and generating mechanical data from them is difficult. Neutron damage can be simulated with ion irradiations but the damage layers are thin – 200nm to 100µm. As such traditional mechanical testing methods cannot be used and novel micro-mechanical tests must be conducted. This leads to difficulties in interpreting the results due to size effects inherent in testing small material volumes.
This project will utilise the newly opened Materials Research Facility at the Culham Centre for Fusion Energy to study the effects of ion irradiation on fusion materials and correlate this with the defect populations produced. This will then be used to develop methods to use small scale mechanical tests to aid engineering design of future fusion systems. Materials of interest include chromium, vanadium and tungsten based alloys.
Ion irradiations will be carried out using protons and heavy ions at a range of international irradiation facilities, at fusion reactor relevant doses and temperatures. Advanced electron microscopy at the Department of Materials, University of Oxford will be used to characterise the damage and defect types produced. Micromechanical tests will be performed at the MRF to understand how these defects affect mechanical behaviour, such as fracture toughness, work hardening, and flow localisation. Tests conducted will include nano-indentation, micro-cantilever and compression tests and micro-scale tensile tests. Finite element modelling will be used to interpret the results. This work will be in close collaboration with a defect based modelling phd based at Oxford Materials, to fully understand the mechanisms which control deformation of irradiated materials.