Measurement of the five-parameter grain boundary distribution from planar sections

Although EBSD is essentially a surface measurement technique, strategies have been developed to extend its capabilities to the char-acterisation of microstructure in three dimensions. These developments have been able to be realised because of advances in both EBSD technology and computing power have rendered the collection of large data sets a routine matter. There are several scientific motivations for characterizing the three-dimensional structure of polycrystals by EBSD. In this Chapter, we describe the application of EBSD to the measurement of internal interface planes by application of both serial sectioning and also a stereological technique known as the 'five-parameter analysis'. An interface (referred to as a grain boundary where it exists between crystals of the same phase) has five geometric degrees of freedom. Usually, three independent parameters are used to describe the misorientation between grains and two independent parameters describe the orientation of the boundary plane (Wolf and Lutsko 1989). Whereas the misorientation is accessed readily by EBSD performed on a single section through the specimen, the boundary plane orientation is not so readily available because the boundary surface itself is buried. Furthermore a single grain boundary, having by definition a fixed misorientation, usually consists of many differently oriented boundary plane segments, as illustrated on Fig. 1. For these reasons measurement of boundary plane crystallography has