In this study, anisotropic ductility and associated damage mechanisms of a grade X100 line pipe steel previously studied at the macroscopic scale were investigated using in situ synchrotron radiation computed tomography of notched round bars. Line pipe materials have anisotropic mechanical properties, such as tensile strength, ductility and toughness. Specimens were tested for loading along both rolling (L) and transverse (T) directions. The in situ data collected allowed quantifying both specimen deformation (evolution of the cross section) and microscopic damage parameters such as porosity, void shape and void orientation. Nucleation at small particles (\({\hbox {CaS/TiO}}_2\)) aligned along the L direction was observed during plastic deformation. It was shown that only very few anisotropic particle clusters are present in the material. However, these clusters led to substantial early void growth for loading normal to the rolling direction, thereby explaining the toughness anisotropy in this material. Significant void growth was observed at the beginning of load decrease for a relatively limited diameter reduction (about 10%). Coalescence of voids within clusters along L direction (Necklace) clearly explained anisotropic rupture.

中文翻译：

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X100管线钢各向异性损伤的起源：第一部分—原位同步加速器层析成像实验

在这项研究中，使用带凹口的圆棒的原位同步辐射X射线断层扫描技术，研究了以前在宏观上研究的X100级管线钢的各向异性延展性和相关的破坏机理。管道材料具有各向异性的机械性能，例如拉伸强度，延展性和韧性。测试了样品沿轧制（L）和横向（T）方向的载荷。收集的原位数据可以量化样品变形（横截面的演变）和微观损伤参数，例如孔隙率，孔隙形状和孔隙方向。沿L排列的小颗粒（\（{\ hbox {CaS / TiO}} _ 2 \）处的成核在塑性变形期间观察到方向。结果表明，材料中仅存在极少数的各向异性颗粒簇。然而，这些团簇导致了在垂直于轧制方向的载荷下大量早期空隙的增长，从而解释了这种材料的韧性各向异性。在载荷减小开始时观察到明显的空隙增长，直径减小相对有限（约10％）。沿L方向（项链）的簇内空隙的合并清楚地解释了各向异性破裂。