Evolution of residual stress and crack morphologies during 3D FIB tomographic analysis of alumina

• Published in: Journal of microscopy (Oxford) 2008-05, Vol.230 (2), p.240-251
• Main Authors: ELFALLAGH, F, INKSON, B.J
• Format: Article
• Language: English
• Subjects: Alumina; Cr3+ fluorescence; Cr³⁺ fluorescence; FIB; microindentation; stress; tomography
• ISSN: 0022-2720; 1365-2818
• DOI: 10.1111/j.1365-2818.2008.01981.x

Three-dimensional focused ion beam (FIB) tomography is increasingly being used for 3D characterization of microstructures in the 50 nm-20 μm range. FIB tomography is a destructive, invasive process, and microstructural changes may potentially occur during the analysis process. Here residual stress and crack morphologies in single-crystal sapphire samples have been concurrently analyzed using Cr³⁺ fluorescence spectroscopy and FIB tomography. Specifically, maps of surface residual stress have been obtained from optically polished single-crystal alumina [surface orientation (1 ī 0 2)], from FIB milled surface trenches, from Vickers micro-indentation sites (loads 50 g-300 g), and from Vickers micro-indentation sites during FIB serial sectioning. The residual stress maps clearly show that FIB sputtering generates residual stress changes. For the case of the Vickers micro-indentations, FIB sputtering causes significant changes in residual stress during the FIB tomographic serial sectioning. 3D reconstruction of the crack distribution around micro-indentation sites shows that the cracks observed are influenced by the location of the FIB milled surface trenches due to localized stress changes.