Misorientations and grain-boundary planes of twin boundaries were determined by applying transmission electron microscopic technique to annealed material with an almost random texture. Straight segments on the long sides of twins were associated with {111} planes. It was noted that, during serial sectioning, the inclination of the grain boundary plane within the removed layer was only assumed. The thickness of this layer was expected to be at least 20µ. Over such a distance, several steps of differing size could easily be found at twin boundaries. Due to faceting, twins could form quite different configurations even though twin boundaries appeared as planar interfaces in the 2-dimension cross-section. If such steps appeared in the sectioning direction, the apparent angle did not reflect the actual inclination of the grain boundary plane. The inclination of the grain-boundary plane of each facet could be appreciably different to that calculated from the angles between grain boundary traces in 2 sections. After sectioning, it was already impossible to know whether such facets existed in the removed layer.

TEM Study of Twin Segments in Annealed Copper. O.V.Mishin, X.Huang: Materials Science Forum, 1999, 294-296, 401-4