Micromechanical testing of irradiated nuclear fusion materials

任何未来的核聚变动力系统都依赖于能够承受一些最极端工程环境的材料的发展。这些包括高达1500摄氏度的温度，高能中子的高通量以及等离子体嬗变和注入产生的气体元素的影响。由于努力尽量减少这种反应堆产生的核废料，可用于结构部件的元素是有限的，在许多情况下，缺乏对以太纯材料或合金中发生的基本变形过程的了解，重要的是这些过程如何受到温度，辐射损伤和气体含量的影响。由于中子辐照活动需要很长的时间，再加上与活性材料相关的成本和工作的困难，需要开发在微观尺度上表征辐照材料的可靠方法。这样做有两个好处。首先，它允许从小体积中子辐照材料中返回最大的数据。其次，它允许使用重离子辐照来模拟中子损伤。在这种情况下，虽然损伤与中子相似，并且可以在更短的时间内形成，但损伤仅超过10微米。这就排除了传统机械测试方法的使用。虽然了解微尺度塑性变形所需的方法已经发展得很好，但微断裂测试却落后了。该项目将以MFFP和微力学小组在微纳米尺度高温断裂测试方面的专业知识为基础。设备包括两个高温纳米压头（-50℃至950℃），高温显微硬度（RT至1500℃）和专用的FIB-SEM和fg - sem与EBSD以及高性能建模站。纳米压痕、微压缩和微弯曲实验将用于钨及钨合金弹塑性断裂的研究。了解这些合金的脆性破坏是安全设计核聚变反应堆关键部件（如分流器）的关键。目前的分流器设计采用钨作为等离子体面组件。然而，对辐照损伤对钨的脆性到延性转变温度的影响的了解很少（只有两个先前的研究-两者都缺乏完整的实验细节在已发表的形式中）。HR-EBSD和TKD将用于研究在测试过程中裂纹尖端周围产生的位错变形结构，并为基于有限元和离散位错动力学模型的晶体塑性提供信息。这门新科学将涉及到强大的弹塑性断裂测试方法的发展，以及对钨和钨合金在强辐照或气体注入前后变形的潜在物理的更全面的理解。这项工作将包括通过融合CDT与CCFE-UKAEA合作。EPSRC的主题和研究领域是能源

Any future nuclear fusion power systems rely on the development of materials which can withstand some of the most extreme engineering environments. These include temperatures up to 1500oC, high fluxes of high energy neutrons and effects of gaseous elements produced by transmutation and implantation from the plasmas. Due to efforts to minimise the production of nuclear waste by such reactors the elements which may be used in structural components is limited and in many cases there is a lack of understanding of the basic deformation processes occur in ether pure materials or alloys and importantly how these are effected by temperature, radiation damage and gas content. Due to the long time periods required for neutron irradiation campaigns, plus the associated cost and difficulty of working with active materials there is a need to develop robust methods for the characterisation of irradiated materials on the microscale. There are two advantages to this. Firstly it allows the maximum data return from small volumes of neutron irradiated materials. Secondly it allows the use of heavy ion irradiation to mimic neutron damage. In this case while the damage is similar to that of neutrons and can be built up in much shorter time frames the damage is only over a few 10's of microns. This precludes the use of traditional mechanical testing methods. While the methods required for understanding micro-scale plastic deformation are well developed micro-fracture testing has lagged behind. This project will build upon the expertise in the MFFP and Micromechanics groups on high temperature frcature testing at the micro and nano-scale. Facilities include two high temperature nanoindenters (-50oC to 950oC), high temperature microhardness (RT to 1500oC) and dedicated FIB-SEM and FEG-SEM with EBSD as well as high performance modelling stations. Both nanoindentation, micro-compression and micro-bend experiments will be used to study elastic-plastic fracture in tungsten and tungsten alloys. Understanding brittle failure of these alloys is key for the safe design of critical fusion reactor components such as the divertor. Currently diverter designs assume tungsten as the plasma facing components. However there is minimal understanding (only two previous studies-both lacking full experimental details in the published form) on the effect of irradiation damage on the brittle to ductile transition temperature in tungsten.HR-EBSD and TKD will be used to study the dislocation deformation structures produced around the crack tips during testing and to inform crystal plasticity based finite element and discrete dislocation dynamics models. The new science will concern both the development of robust elastic-plastic fracture testing methodologies as well as a the fuller understanding of the underlying physics of deformation in tungsten and tungsten alloys both before and after heavy irradiation or gas implantation. The work will include collaboration with CCFE-UKAEA through the fusion CDT.EPSRC theme and research area is Energy