Indentation size effect and dislocation structure evolution in (001) oriented SrTiO3 Berkovich indentations: HR-EBSD and etch-pit analysis
Indentation size effect and dislocation structure evolution in (001) oriented SrTiO3 Berkovich indentations: HR-EBSD and etch-pit analysis
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DOI：
10.1016/j.actamat.2017.07.055
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发表时间：
2017-10
期刊：
影响因子：
9.4
通讯作者：
Farhan Javaid;E. Bruder;K. Durst
中科院分区：
文献类型：
--
作者：
Farhan Javaid;E. Bruder;K. Durst
本文采用顺序抛光、化学蚀坑技术和高分辨电子背散射衍射（HR-EBSD）技术，通过Berkovich纳米压痕实验研究了（001）取向STO中位错结构的演化和压痕尺寸效应。纳米压痕的载荷-位移曲线显示了多个弹出事件，这与残余压痕周围位错堆积的成核和延伸有关。顺序抛光和蚀刻揭示了在不同的亚表面深度的三维位错蚀坑结构。通过HR-EBSD和蚀坑分析确定了表面以下5 mN和10 mN压痕的位错密度。与HR-EBSD，晶格旋转，从而GND密度确定，而蚀坑技术揭示了总位错密度。基于独立测量的位错密度，我们清楚地表明了深度依赖的位错密度，总密度和GND密度随着压痕深度的减小而增加。较小压痕下较高的位错密度解释了观察到的STO硬度的尺寸依赖性，这也揭示了STO中高压痕硬度和低屈服强度的非凡组合。
In the present work, the dislocation structure evolution and indentation size effect in (001) oriented STO have been studied by using sequential polishing, chemical etch-pit technique and high-resolution electron backscattered diffraction (HR-EBSD) analysis via Berkovich nanoindentation experiments. Nanoindentation load-displacement curves show multiple pop-in events, which relate to nucleation and extension of dislocation pile-ups around the residual impression. Sequential polishing and etching revealed the three-dimensional dislocation etch-pit structure at various sub-surface depths. The dislocation densities are determined for a 5 mN and 10 mN indentation below the surface via HR-EBSD and etch-pit analysis. With HR-EBSD, the lattice rotation and thereby GND densities are determined, while the etch-pit technique revealed the total dislocation density. Based on the independently measured dislocation densities, we clearly show a depth dependent dislocation density, where both total and GND densities increase with decreasing indentation depths. The higher dislocation densities below smaller indents explain the observed size dependency of the hardness in STO, which also sheds light on the extraordinary combination of high indentation hardness and low yield strength in STO.