Micromechanical Testing of Irradiated Nuclear Fusion Materials

了解中子辐照损伤如何影响结构材料的机械性能是实现核聚变作为可持续能源的关键一步。然而，研究辐照材料的成本很高，从这些材料中生成机械数据也很困难。中子损伤可以用离子辐照来模拟，但损伤层很薄-200 nm到100微米。因此，不能使用传统的机械测试方法，必须进行新的微观机械测试。由于在测试小体积材料时固有的尺寸效应，这导致很难解释结果。这个项目将利用库勒姆聚变能源中心新开放的材料研究设施(MRF)来研究离子辐照对聚变材料的影响，并将其与产生的缺陷数量联系起来。然后，这将被用来开发使用小规模机械测试的方法，以帮助未来聚变系统的工程设计。感兴趣的材料包括铁、铬、钒和钨基合金，该方案最初将重点放在铁铬合金上。将在一系列国际辐照设施中以聚变反应堆相关剂量和温度使用质子和重离子进行离子辐照。牛津大学材料系的先进电子显微镜将被用来表征所产生的损伤和缺陷类型。将在MRF进行微观机械测试，以了解这些缺陷如何影响机械性能，如延展性、加工硬化和流动局部化。进行的测试将包括微型拉伸或压缩测试，包括在MRF的扫描电子显微镜下进行现场测试。数字图像相关将用于量化在变形过程中发展的塑性滑移模式，特别关注辐照如何降低变形的均匀性和增加滑移带中的局部应变强度。高分辨率的EBSD将被用来绘制在整个测试过程中间歇性间隔的位错密度和应力分布。有限元模型将被用来帮助解释结果，并捕捉我们对变形模式的理解。该项目是与库勒姆聚变能源中心合作的，DPhil的学生将成为EPSRC聚变科学与技术CDT的一部分。该研究方案与EPSRC的“能源”组合主题以及“聚变”和“核能”分主题保持一致。“工程”这一主题也与“材料工程--金属和合金”研究领域相关。

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 - 200 nm to 100 microns. 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 (MRF) 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 iron, chromium, vanadium and tungsten based alloys and this programme will initially focus on iron - chromium 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 ductility, work hardening, and flow localisation. Tests conducted will involve micro-scale tensile or compression testing including testing in situ in the scanning electron microscope at the MRF. Digital image correlation will be used to quantify the pattern of plastic slip that develops during deformation with particular focus on how irradiation decreases the deformation homogeneity and increases the local strain intensities in slip bands. High resolution EBSD will be used to map the dislocation density and stress distributions at intermittent intervals throughout such tests. Finite element modelling will be used to help interpret the results and capture our understanding of the deformation patterning. The project is in collaboration with the Culham Centre for Fusion Energy and the DPhil student will be part of the EPSRC CDT on the Science & Technology of Fusion. The research programme aligns with the EPSRC portfolio themes of both 'Energy' and the sub-themes 'Fusion' and 'Nuclear Power'. The 'Engineering' theme is also relevant through the 'Materials Engineering - Metals and Alloys' research area.