Surface patterning for combined digital image correlation and electron backscatter diffraction in-situ deformation experiments

Abstract

A considerable amount of information can be gained from combined collection of both digital image correlation (DIC) measurements, and of electron backscattered diffraction (EBSD) data from the same area during in-situ deformation experiments. Such data collection remains a challenge, however, due the influence of the surface markers required for DIC on the EBSD data quality. In this work we demonstrate that by careful control of the sample preparation process, a two-step electropolishing method can be used to generate excellent surface markers for DIC where the markers are integral features on the surface. The method does not require any special equipment and can be used to collect high quality EBSD data and DIC data with sub-micron resolution on the same area during repeated loading as part of in-situ deformation experiments. Combined EBSD and DIC measurements are illustrated in this work for samples of Al deformed in tension to a strain of 10%. Due to the integral nature of the surface markers we demonstrate also that it is possible to perform DIC measurements up to large plastic strains, including the necked region within a tensile sample. A comparison of EBSD and DIC data collected from the same area of a tensile-deformed sample shows that although the EBSD data provide excellent information on the lattice rotations developed during deformation, these data cannot be directly used as a measure of local plastic strain on the scale of the deformation microstructure. The ability to collect both EBSD and DIC data during an in-situ experiment provides, therefore, an opportunity to explore further the complex relationship between local plastic strain heterogeneity and EBSD-based measures of crystal lattice rotation.