Grain boundary migration in polycrystalline -Fe

High energy x-ray diffraction microscopy was used to image the microstructure of alpha-Fe before and after a 600 degrees C anneal. These data were used to determine the areas, curvatures, energies, and velocities of approximately 40,000 grain boundaries. The measured grain boundary properties depend on the five macroscopic grain boundary parameters. The velocities are not correlated with the product of the mean boundary curvature and grain boundary energy, usually assumed to be the driving force. The total migration of a boundary consists of both translations approximately normal to the boundary and lateral changes in area. Through the lateral changes in area, low energy boundaries tend to expand in area while high energy boundaries shrink, reducing the average energy through grain boundary replacement. The driving force for this process is not related to curvature and might disrupt the expected curvature - velocity relationship.