Multiscale Characterisation Of Creep Deformation Of Materials For Fusion Reactors.

由于聚变反应堆中的极端条件，材料性能是聚变电厂未来生产的关键因素。结构材料必须长期经受高温和严重的辐射损伤，因此蠕变是一种关键的失效机制，需要在基础上迅速发展。用于聚变的材料技术准备程度低，新颖，只能小批量供应。因此，需要从给定数量的材料中提取尽可能多的信息。该项目的目标是致力于对蠕变状态下的材料行为进行研究，主要使用91级钢作为EUROFER 97的模型材料。这项工作将利用图像处理技术数字图像相关(DIC)固有的可扩展性，利用扫描电子显微镜(SEM)的可见光和电子成像的组合，同时在同一样品上量化多个长度尺度上的蠕变变形。与单轴试验相比，大尺度的DIC将有助于将样品设计为经历空间应力梯度，减少表征蠕变行为所需的材料量。微结构尺度DIC将被用来观察样品所经历的应力状态范围内的颗粒尺度现象。这种测试尺度的组合将使宏观尺度行为能够通过颗粒尺度行为来解释，从而对材料的蠕变机制和失效模式产生更微妙的洞察。这是可以实现的，因为开放大学独特的DIC监测蠕变测试设施，以及开放大学和英国AEA在微结构规模DIC方面的现有专业知识。

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.