Using SEM-DIC to Examine Phase Transformation and Other Strain Localization Phenomena At the Microscale

A new methodology for the study of phase transformation in shape memory alloys and other heterogeneously deforming materials at the length scale of the microstructure is discussed. A combination of Scanning Electron Microscopy (SEM) and Digital Image Correlation (DIC), termed here as SEM-DIC, has been used to successfully track the microstructural strains (indicative of the extent of phase transformation) in Nickel-Titanium with subpixel accuracy. This talk will provide details on the challenges associated with the application of the methodology and offer insights on addressing these challenges.  The methodologies we have developed for small-scale DIC patterning at varied fields of view, the removal of the complex spatial and temporal distortions from SEM imaging prior to strain calculation, and the correct alignment of the SEM-DIC strain maps with underlying crystallographic structure from Electron Backscatter Diffraction (EBSD) will be given special attention. Results and analysis of in situ investigations of superelastic Nickel-Titanium will be used as an example of the unique information that can be obtained from this approach.