In-situ studies of strain accommodation in MAX phase materials for advanced nuclear energy

MAX相是二维层状六方碳化物或氮化物，在高温下可以表现出非常高的机械损伤容限。与陶瓷一样，它们在快中子照射下的活性明显低于金属。因此，它们在先进核裂变的结构应用中具有潜在的应用。然而，需要更好地了解MAX阶段的结构/性能关系和损伤累积机制，以基于微观结构的建模来支持材料和工程部件的设计和开发。图像分析和衍射的应变映射使结构材料中的变形研究发生了革命性的变化。它们结合在一起，可以提供复杂结构内的弹性和塑性应变状态的优秀知识，这些结构在内部以高空间分辨率在三维中进行“应变测量”。用于层析成像的图像相关工具可以高精度地测量三维变形和总应变状态。用中子和高能同步X射线光束线进行衍射分析来测量块状材料中的弹性应变也是一种常规方法。该项目的目的是利用X射线和中子衍射和成像技术，在现场和三维测绘载荷和高温下的总应变和弹性应变，从而对核能用大块MAX相材料的应变调节机制进行新的研究，重点研究应变历史、微结构织构和材料非均质性的影响，以提高材料的可靠性和性能。该项目的目标是特别研究TiAlC系统的纯相材料和工业纯相Max相材料之间的差异，包括应用高分辨率电子背散射衍射(EBSD)来研究在加工过程中引入的织构可能会影响应变在颗粒和相之间的传递。该项目与同时开始的一个平行项目密切配合，即利用高温纳米压痕和高分辨率显微镜，在微观尺度上研究用于先进核能的MAX相材料的应变调节。该项目与SCK-CEN(比利时)合作，后者正在与欧洲能源研究联盟核材料联合方案一起开发核应用的最大阶段，该方案旨在为下一代可持续核能开发材料。该项目还与用于先进事故容错能源系统的创新覆层材料的H2020 Il Trovatore方案相联系，在该方案中，SCK-CEN正在进行标准的机械测试(包括辐照材料的研究)，以及EBSD和透射电子显微镜的电子显微镜微结构表征。该项目属于EPSRC能源研究主题(核能)。

MAX phases are 2D-layered hexagonal carbides or nitrides that can exhibit very high mechanical damage tolerance at high temperatures. In common with ceramics, they are significantly less activated than metals by fast neutron irradiation. Hence they have potential applications in structural applications for advanced nuclear fission. However, the structure/property relationships and mechanisms of damage accumulation in MAX phases need to be better understood for microstructure-based modelling to support the design and development of materials and engineering components. Strain mapping by both image analysis and diffraction has revolutionized studies of deformation in structural materials. Together, they can provide excellent knowledge of both the elastic and plastic strain states within complex structures, which are internally "strain gauged" in three-dimensions with high spatial resolution. Image correlation tools applied to tomographs can measure three-dimensional deformation and total strain states with high precision. Diffraction analysis to measure elastic strains within bulk materials is also routine with neutrons and also on high energy synchrotron X-ray beam-lines. The project aims to use X-ray and neutron diffraction and imaging to map, in situ and in 3D, both the total and elastic strains under load and at elevated temperature, and thereby perform novel studies of the mechanisms of strain accommodation in bulk MAX phase materials for nuclear energy, with emphasis on the effects of strain history, microstructure texture and material heterogeneity, in order to improve material reliability and performance. The objectives of the project are to study, in particular, the differences between phase pure and commercial purity MAX phase materials from the TiAlC system, including the application of high resolution electron backscatter diffraction (EBSD) to study the transfer of strain between grains and phases, which may be affected by the texture that is introduced during processing. This project interacts closely with a parallel project, starting at the same time, that is conducting studies of strain accommodation in MAX phase materials for advanced nuclear energy at the microscale, using high temperature nano-indentation and high resolution microscopy. This project collaborates with SCK-CEN (Belgium) who are developing MAX phases for nuclear applications in conjunction with the European Energy Research Alliance Joint Programme in Nuclear Materials that aims to develop materials for next generation sustainable nuclear energy. The project also connects with the H2020 Il Trovatore programme on Innovative cladding materials for advanced accident-tolerant energy systems, in which standard mechanical testing (including studies of irradiated materials) are being conducted by SCK-CEN, together with electron-microscopy microstructure characterisation by EBSD and Transmission electron microscopy. This project falls within the EPSRC Energy Research Theme (Nuclear Power).