M. Groeber, B. Haley, M. Uchic, and S. Ghosh

In this work, a new technique utilizing an automated approach of combining a Focused Ion Beam (FIB) and Electron Back-Scatter Diffraction (EBSD) system was implemented for the collection of 3-D orientation data that can be used to more accurately model grain and sub-grain particle structures. The process is currently capable of sectioning a sample with inter-slice thicknesses as low as 100 nanometers and capturing an orientation map of each slice. Automation of this technique allowed for rapid data collection with the ability to update settings in real time. The orientation data obtained by the EBSD scans consists of each grid point’s position, three Euler angles and phase. Reconstruction of the 3-D orientation data involves combining or “stacking” the 2-D slices obtained by the FIB-EBSD process. The orientation data of each slice is combined into one data file containing orientation information for each point on the 3-D grid, which can have spacing as little as 100 nanometers in all three directions. A program developed in this work, Micro-Mesher, uses the reconstructed orientation information to define microstructural features such as grains and second phase particles. Micro-Mesher constructs grain boundaries with line and plane segments using an error per unit length approach to approximate the complex grain boundaries. Important microstructural statistics that are used to define and characterize the 3-D microstructure are also calculated by Micro-Mesher. Such important parameters include: grain size, no. of neighboring grains, orientations and misorientations, no. of faces, and second phase particles size as well as others. The 3-D statistical information gained from this process improves the ability to accurately characterize the microstructure.