Abstract text (incl. figure legends and references)

Abstract

In experimental mechanics, the digital image correlation (DIC) technique using scanning transmission electron microscope (SEM) images has been extensively used for quantitative deformation analysis [1]. In order to increase the sensitivity of DIC toward nanoscale strain detection, efforts are made to couple the DIC with transmission electron microscopy (TEM) images. At present, there are only a few experimental DIC studies available based on TEM [2, 3], hence exploiting this direction on various materials is desirable. In the present work, the grain boundary sliding deformation mechanism in olivine is investigated through the DIC technique coupled with TEM to get enhanced spatial resolution for mapping the small localized strain onset of the grain boundary sliding. For this purpose, forsterite nano-tensile specimens containing a single grain boundary or a triple point are prepared from synthetic forsterite (Mg-rich end member of olivine) by focused ion beam (FIB) after grain orientation mapping using ASTAR (see Fig. 01). Further, the surface of the tensile samples is decorated with nano-Pt particles during FIB. The in-situ nanomechanical test performed inside TEM uses high-angle annular dark field (HAADF) imaging to minimize the dynamical contrast. We demonstrate that during the deformation, strain localized at the grain boundaries triggers the sliding activity. These full-field quantitative nanoscale deformation investigations provide insight into the mechanisms that influence the macroscopic response.

[1] A. Weidner and H. Biermann, "Review on Strain Localization Phenomena Studied by High-Resolution Digital Image Correlation," Adv. Eng. Mater., vol. 23, no. 4, 2021, doi: 10.1002/adem.202001409.

[2] X. Wang, Z. Pan, F. Fan, J. Wang, Y. Liu, Scott X. Mao, T. Zhu, and S. Xia, "Nanoscale deformation analysis with high-resolution transmission electron microscopy and digital image correlation," J. Appl. Mech. Trans. ASME, vol. 82, no. 12, pp. 1–9, 2015, doi: 10.1115/1.4031332.

[3] Y. Zhang, L. Feng, S. Dillon, and J. Lambros, "Full-field deformation measurements in the transmission electron microscope using digital image correlation and particle tracking," Mater. Charact., vol. 183, no. July 2021, p. 111598, 2022, doi: 10.1016/j.matchar.2021.111598.

Fig. 01 Sample preparation and in-situ TEM nanomechanical experiment (a) FIB lamella showing the different grain boundaries and inset showing the ACOM-TEM from the selected area for cutting the tensile specimen (b) Push-To-Pull (PTP) device for in-situ TEM. A diamond flat punches the semicircular end on the top and opens the middle gap to strain the specimen. Inset shows the forsterite tensile specimen having a triple junction grain boundary before the fracture.