5D Grain Boundary Characterization from EBSD Microscopy

Akash Savio Amalaraj, Brigham Young University


Knowledge of the full 5-degree Grain Boundary Character Distribution (GBCD) is vital to understanding properties, such as gas diffusivity, that are dominated by grain boundary character. Surface characterization techniques, such as Electron Backscattered diffraction (EBSD), can provide only 4 of the 5 GB characteristics (the rotation between the neighboring grains, and the trace of the GB on the surface). The inclination of the GB in the direction normal to the surface is not known. A previous study indicated that the GB inclination could be recovered by correlating the Electron Backscattered patterns (EBSPs) of sample points near the GB with EBSPs taken from the centers of the neighboring grains. The resultant transition curve could be compared with theoretical curves obtained from MonteCarlo simulations of electron yield from the two grains. However, a practical method based upon this study was never implemented. Here, a few microscopy and image filters have been applied to the EBSPs to improve the image quality. Also, several experiments have been conducted to verify and validate the interaction volume of the materials used to produce theoretical transition curves, in order to receive more accurate results. In this work, it is hypothesized that transition curves obtained from considering individual band intensities from the EBSPs will give more informative transition curves. The filtered EBSPs from the band intensities coupled with the accurate interaction volume values, should give us more reliable and repeatable transition curves, and that a more detailed comparison of the experimental and simulated transition curves will give higher fidelity results, in terms of GB inclination determination.