In situ measurement of elastic and total strains during ambient and high temperature deformation of a polygranular graphite
In situ measurement of elastic and total strains during ambient and high temperature deformation of a polygranular graphite
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DOI：
10.1016/j.carbon.2020.03.020
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发表时间：
2020-08
期刊：
影响因子：
10.9
通讯作者：
Dong Liu;T. Zillhardt;P. Earp;S. Kabra;Thomas Connolley;T. James Marrow
中科院分区：
文献类型：
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作者：
Dong Liu;T. Zillhardt;P. Earp;S. Kabra;Thomas Connolley;T. James Marrow
利用原位中子衍射和同步加速器x射线衍射，结合二维光学和三维x射线断层成像数据集的图像相关分析，研究了Gilsocarbon （IM1-24）多颗粒核级石墨变形过程中弹性晶格应变与总应变的关系。试件在直径荷载作用下呈平端巴西盘状，中部呈压缩-拉伸双轴应力状态。x射线研究在环境温度下进行，中子衍射在环境至850℃的温度下进行。在压缩条件下，总应变与垂直于石墨基面的晶格应变之间存在温度不敏感的线性关系。而在拉应力作用下，总应变与弹性应变关系对温度敏感：在600℃以下，晶格拉伸应变随着总拉伸应变的增大而趋于饱和；在600°C以上，晶格拉伸应变明显较高。拉伸点阵应变的饱和是由石墨微观组织的微裂纹引起的。在高温下抗微裂和损伤容忍度的提高解释了多颗粒石墨抗拉强度的增加。
In situneutron 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.