Precession Illumination Based Orientation Imaging, Grain Size and Defect Analysis in the Transmission Electron Microscope

We use computer-controlled TEM orientation imaging microscopy (TEM-OIM) to measure grain sizes, orientation distributions, grainboundary and dislocation character with nanometer resolution. This TEM-OIM involves automated acquisition and indexing of precession illumination diffraction patterns and enables facile analysis of orientation maps akin to those popularized by SEM-EBSD based OIM. The probe size of the TEM instrument determines the lateral resolution of TEMOIM to ~1-2 nm for field emission guns and ~15nm for LaB6 guns. Additionally, precession illumination hollow cone dark field imaging has been used for enhanced efficiency grain size measurements even in nanocrystalline aggregates. Finally, precession diffraction based virtual dark field imaging mode introduced for dislocation analysis. Results of orientation and grain size distribution measurements in nanocrystalline Ni and rapidly solidified Al thin films and for Burgers vector analyses in deformed NiAl and TiAl samples will be presented and discussed.