Multiscale high-temperature mechanical performance of materials for nuclear fusion

核聚变现在正被认真考虑作为2050年后的未来能源，正如最近宣布在新罕布什尔州建造STEP所证明的那样。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。如果不了解中子损伤对材料的影响，就没有现实的方法来使反应堆的组件寿命延长。然而，我们不能仅仅建造一个反应堆来测试材料，然而，在辐照材料上工作是昂贵的，并且很难从中产生机械数据。中子损伤可以用离子辐照来模拟，但损伤层很薄- 200 nm至100 um。因此，传统的力学测试方法无法使用，必须进行新的微观力学测试。由于测试小材料体积时固有的尺寸效应，这导致难以解释结果。正在开发的机械模型，将包括辐射损伤的影响，不断发展的机械性能，但这些需要大量的实验输入的表征和机械的理解，不同的微观结构特征（空隙，沉淀物，环路）如何控制辐射诱导硬化的形式。该项目的目标是利用一系列模型合金的微观力学测试，以消除不同微观结构特征的影响。合金将被铸造成具有受控水平的铬、碳和钒，以允许控制固溶体、间隙和碳化物强化。样品将用重离子和氦辐照以产生空隙和位错环。硬化将在室温和工作温度下使用纳米压痕进行研究。室温下的纳米压痕是研究辐照硬化的标准方法，但使用纳米压痕进行高温辐照硬化的工作要少得多。我们期望使用牛津大学发展起来的新的计算塑性有限元法，我们将看到辐照损伤不仅对屈服应力而且对加工硬化的影响。要了解这两个起始的微观结构，在辐照下的微观结构的演变和相互作用的滑移位错与微观结构特征先进的电子衍射成像将被使用。这将包括衍射对比TEM，这是建立良好的研究这样的微观结构，也是传输菊池衍射，这是很少应用于研究辐射损伤，但具有更简单，更便宜的成像设备的优势。我们希望在项目结束时，我们将有一系列的微观结构，辐照它们，机械测试它们，并将硬化与观察到的微观结构联系起来。然后将其输入到UKAEA新开发的模型中。该项目是在与UKAEA/卡勒姆中心聚变能源和哲学博士的学生将是EPSRC CDT的科学与聚变技术的一部分合作。该研究计划与EPSRC的组合主题“能源”和子主题“聚变”和“核能”保持一致。“工程”主题也与“材料工程-金属和合金”研究领域相关。

Nuclear fusion is now being seriously considered as future power source for post 2050, as demonstrated by the recent announcement of the STEP construction in Nottinghamshire. 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. Without understanding the effect that neutron damage has on the materials there is not realistic method of lifing components hence reactors. However we cannot just build a reactor to test materials and 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 um. 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. Mechanical models are being developed that will include the effect of irradiation damage on the evolving mechanical properties, but these require substantial experimental input in the form of characterisation and mechanistic understanding of how different microstructural features (voids, precipitates, loops) control irradiation induced hardening. This project will aim to use micromechanical testing on a series of model alloys to deconvolute the effects of different microstructural features. The alloys will be cast with controlled levels of chromium, carbon, and vanadium, to allow control of solid solution, interstitial and carbide strengthening. Samples will be irradiated with both heavy ions and helium to generate voids and dislocations loops. Hardening will be studied using nanoindentation at both room and operational temperatures. Nanoindentation at room temperature is a standard method of studying irradiation hardening but much less work has been carried out on high temperature irradiation hardening using nanoindentation. We expect that using newly developed computational plasticity finite elements methods developed in oxford we will see the effect off irradiation damage not just on yield tress but also work hardening. To understand both the starting microstructure, the microstructural evolution under irradiation and the interaction of the glissile dislocations with microstructural features advanced electron diffraction imaging will be used. This will include diffraction contrast TEM which is well established for studying such microstructures and also transmission Kikuchi diffraction which is much less applied to studying radiation damage but has the advantage of simpler and cheaper imagining equipment. We expected that byt the end of the project we will have gnateatered a range of microstructures, irradiated them, mechanically tested them and related the hardening to the observed microstructures. This will then be inputed to newly developed models at UKAEA. The project is in collaboration with the UKAEA/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.