An x-ray diffraction and computer simulation study of [111] twist boundaries in gold

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Abstract
Quantitative X-ray diffraction measurements have been made from a series of (111) gold bicrystals containing twist grain boundaries with controlled geometry. Each bicrystal was prepared at a specific angle of misorientation Θ° but because of double positioning both Θ° and 60-Θ° twist boundaries were present in the specimens. Since these pairs of boundaries have distinct structures, the intensity measurements from each bicrystal contained superimposed information representing an average from both boundary types. In order to understand these measurements in terms of the boundary structures involved, computer calculations were performed to characterize the theoretical scattering effects expected from [111] twist boundaries related by double positioning. By comparing the measurements with the calculations, it was possible to determine the conditions under which reliable structural information concerning doubly positioned twist boundaries could be obtained. From an appropriate analysis of the data, it was concluded that [111] twist boundary displacement fields are generally weak, rotational in form, and centred on ‘0’ lattice sites.