The variation of grain boundary structural width with misorientation angle and boundary plane

Abstract

An important characteristic of a grain boundary is the depth to which its displacement field penetrates into the neighbouring single crystals. This boundary thickness, which is called the ‘structural width’ in this paper, may be studied by the use of an electron diffraction technique which is sensitive to the width of the region of large strain at the boundary. The periodic structure of a grain boundary gives rise to extra reflections and, since these are associated only with the thin boundary region, they are elongated into relrods along the direction normal to the boundary plane. By selecting boundaries which are parallel to the electron beam, these relrods may be cut along their length by the Ewald sphere; the length of the resulting streaks in the diffraction pattern is inversely related to the grain boundary structural width. Edge-on tilt boundaries with an [001] tilt axis have been studied in manufactured gold bicrystals for misorientation angles from 3.5° to 36.9°, and for (100) and (110) boundary planes. The value obtained for structural width for all the boundaries is shown to be related in almost all cases to the magnitude of the O-lattice periodicity associated with the misorientation.