Multiscale Characterisation Of Creep Deformation Of Materials For Fusion Reactors.

Due to the extreme conditions seen in a fusion reactor, material performance is a critical factor in the future production of fusion power plants. Structural materials must survive high operating temperatures and severe irradiation damage for long periods of time, and so creep is a critical failure mechanism that requires rapid development in fundamental understanding.

Materials for fusion are low technology readiness level, novel and only available in small volumes. Therefore, there is a need to extract as much information from a given amount of material as possible. The aim of this project is to work towards doing just that for material behaviour in the creep regime, primarily using Grade 91 steel as a model material for EUROFER 97. This work will utilise the inherent scalability of the image processing technique Digital Image Correlation (DIC) to quantify creep deformation at multiple length scales concurrently on the same sample, using a combination of visible light and electron imaging using a scanning electron microscope (SEM). The macroscale DIC will facilitate the sample to be designed to experience a spatial stress gradient, reducing the amount of material required to characterise creep behaviour when compared to uniaxial testing. The microstructural scale DIC will be used to observe grain scale phenomena across the range of stress states experienced by the sample. This combination of test scales will enable macroscale behaviour to be explained by grain-scale behaviour, developing a more nuanced insight into the material's creep mechanisms and failure modes. This is achievable due to the unique DIC-monitored creep testing facilities at the Open University and the existing expertise at Open University and UKAEA in microstructural-scale DIC.