Abstract In situ neutron diffraction and synchrotron X-ray diffraction, combined with image correlation analysis of 2D optical and 3D X-ray tomography datasets, have been used to investigate the relationship between elastic lattice strain and total strain during deformation of Gilsocarbon (IM1-24) polygranular nuclear grade graphite. The specimens were flat-end Brazilian discs under diametral loading, such that a compressive-tensile biaxial stress state was developed in the central region. The X-ray study was at ambient temperature, and the neutron diffraction was conducted at temperatures from ambient to 850 °C. When under compression, there is a temperature-insensitive linear relationship between the total strain and the lattice strain that is measured perpendicular to the graphite basal planes. However, when under tensile stress, the total strain and elastic strain relationship is temperature sensitive: below 600 °C, the lattice tensile strain saturates with increasing total tensile strain; above 600 °C, significantly higher tensile lattice strains are sustained. The saturation in tensile lattice strain is attributed to microcracking in the graphite microstructure. Improved resistance to microcracking and damage tolerance at elevated temperature explains the increase in tensile strength of polygranular graphite.

中文翻译：

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多颗粒石墨在环境和高温变形期间的弹性应变和总应变的原位测量

摘要 原位中子衍射和同步加速器 X 射线衍射，结合 2D 光学和 3D X 射线断层扫描数据集的图像相关性分析，已被用于研究 Gilsocarbon (IM1-24) 变形过程中弹性晶格应变与总应变之间的关系。 ) 多粒核级石墨。试样是在径向载荷下的平端巴西圆盘，因此在中心区域形成压缩-拉伸双轴应力状态。X 射线研究在环境温度下进行，中子衍射在环境温度至 850 °C 的温度下进行。当处于压缩状态时，总应变和垂直于石墨基面测量的晶格应变之间存在温度不敏感的线性关系。然而，当受到拉应力时，总应变和弹性应变的关系是温度敏感的：低于 600 °C，晶格拉伸应变随着总拉伸应变的增加而饱和；高于 600 °C，显着更高的拉伸晶格应变得以维持。拉伸晶格应变的饱和归因于石墨微观结构中的微裂纹。提高的抗微裂纹性和高温损伤容限解释了多颗粒石墨拉伸强度的增加。