Kondo Shun, Ishihara Akihito, Tochigi Eita, Shibata Naoya, Ikuhara Yuichi
Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan.
Center for Elements Strategy Initiative for Structural Materials, Kyoto University, Kyoto, 606-8501, Japan.
Nat Commun. 2019 May 8;10(1):2112. doi: 10.1038/s41467-019-10183-3.
In fracture processes, grain boundaries behave as preferential paths for crack propagation. These grain boundary fractures proceed by the atomic-bond rupture within the grain boundary cores, and thus grain boundary structures have crucial influence on the fracture properties. However, the relationship between grain boundary structures and atomic fracture processes has been a matter of conjecture, especially in the case of dopant-segregated grain boundaries which have complicated local structures and chemistries. Here, we determine the atomic-bond breaking path within a dopant-segregated AlO grain boundary core, via atomic-scale observations of the as-fractured surface and the crack tip introduced by in situ nanoindentation experiments inside a transmission electron microscope. Our observations show that the atomic fracture path is selected to produce less coordination-deficient oxygen polyhedra of dopant cations, which is rationalised using first-principles calculations. The present findings indicate that the atomic coordination geometry at the grain boundary core affects the fracture processes.
在断裂过程中，晶界充当裂纹扩展的优先路径。这些晶界断裂通过晶界核心内的原子键断裂而发生，因此晶界结构对断裂性能有至关重要的影响。然而，晶界结构与原子断裂过程之间的关系一直是个猜测的问题，特别是在掺杂剂偏析的晶界情况下，其具有复杂的局部结构和化学性质。在此，我们通过对断裂表面和透射电子显微镜内原位纳米压痕实验引入的裂纹尖端进行原子尺度观察，确定了掺杂剂偏析的AlO晶界核心内的原子键断裂路径。我们的观察表明，原子断裂路径的选择是为了产生掺杂剂阳离子的配位缺陷较少的氧多面体，这通过第一性原理计算得到了合理的解释。目前的研究结果表明，晶界核心处的原子配位几何形状会影响断裂过程。
