ACCURATE DETERMINATION OF THE DEVIATION FROM COINCIDENCE ORIENTATION FOR GRAIN-BOUNDARIES IN HEXAGONAL MATERIALS

Accurate measurement of the deviation from coincidence orientation for grain boundaries allows the intergranular dislocation structure to be predicted. For hexagonal symmetry, the deviation may generally be split into two components: a pure rotation and a deformation. This rotation may be determined directly by measuring the displacement of rational common zone axes across the grain boundary plane, independently of any coincidence site lattice (CSL). The precision on the elements of the rotation - axis and angle - depends strongly on the sharpness of the Kikuchi lines. For deformed and annealed magnesium, a precision of 10-degrees on the axis position and of 0.2-degrees on the rotation angle has been obtained.