ON THE POSSIBLE MULTIPLICITY OF NEARLY EQUIVALENT COINCIDENCE SITE LATTICES FOR (0(1)OVER-BAR-12) TWIN IN HEXAGONAL CRYSTALS

Features of secondary dislocation networks lying in a near coincidence grain boundary may be predicted as a function of the misorientation, i.e. the deviation from exact coincidence orientation. This work was c arried out for the (0112BAR) common twin in magnesium in case of devia tions from several CSLs close to the twin orientation. The dislocation line direction and spacing associated with basis and combined DSC vec tors are calculated for a range of deviations. It is shown that for sm all deviation angles, the dislocation networks associated with differe nt CSLs may be distinguished which allows the CSL adopted by the grain boundary to be discriminated. By using the criterion of the lowest di slocation density, some CSLs are favoured as a function of the deviati on.