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.
Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.
Sci Adv. 2016 Nov 11;2(11):e1501926. doi: 10.1126/sciadv.1501926. eCollection 2016 Nov.
In deformation processes, the presence of grain boundaries has a crucial influence on dislocation behavior; these boundaries drastically change the mechanical properties of polycrystalline materials. It has been considered that grain boundaries act as effective barriers for dislocation glide, but the origin of this barrier-like behavior has been a matter of conjecture for many years. We directly observe how the motion of individual dislocations is impeded at well-defined high-angle and low-angle grain boundaries in SrTiO, via in situ nanoindentation experiments inside a transmission electron microscope. Our in situ observations show that both the high-angle and low-angle grain boundaries impede dislocation glide across them and that the impediment of dislocation glide does not simply originate from the geometric effects; it arises as a result of the local structural stabilization effects at grain boundary cores as well, especially for low-angle grain boundaries. The present findings indicate that simultaneous consideration of both the geometric effects and the stabilization effects is necessary to quantitatively understand the dislocation impediment processes at grain boundaries.
在变形过程中，晶界的存在对位错行为有至关重要的影响；这些晶界极大地改变了多晶材料的力学性能。人们一直认为晶界对位错滑移起到有效的阻碍作用，但这种阻碍作用的起源多年来一直是推测的问题。我们通过在透射电子显微镜内进行原位纳米压痕实验，直接观察到单个位错在 SrTiO3 中确定的高角度和低角度晶界处的运动是如何受阻的。我们的原位观察表明，高角度晶界和低角度晶界都阻碍位错穿过它们的滑移，而且位错滑移的阻碍并不仅仅源于几何效应；它还源自晶界核心的局部结构稳定化效应，尤其是对于低角度晶界。这些发现表明，为了定量理解晶界处位错阻碍过程，同时考虑几何效应和稳定化效应是必要的。
