The coincidence site lattice and the ‘sigma enigma’

This paper focuses on the most appropriate use of electron back-scatter diffraction (EBSD) post-acquisition analysis for categorisation of grain boundaries in polycrystals. A brief survey of the early literature shows that the most meaningful reference structure for grain boundaries in polycrystals is periodicity in the grain boundary surface, rather than the misorientation-based coincidence site lattice (CSL) and Σ notation. However, use of the CSL is convenient to the experimentalist. It is therefore suggested that wherever possible, misorientation data, obtained by EBSD mapping and classified according to CSL types, should be supplemented with other, more detailed information to aid analysis.