Grain-boundary structures in polycrystalline metals at the nanoscale

摘要: We present a detailed analysis of grain-boundary structures in computer-generated Cu and Ni three-dimensional nanocrystalline samples. The study includes both totally random textured microstructures with grain sizes the range 5\char21{}12 nm. A direct visualization technique is used at atomic scale for studying structural features. focuses on determining presence regions boundary exhibiting order units normally expected high-angle boundaries. For low-angle boundaries we investigate dislocation networks accommodating misfit between grains. significant degree crystalline found all studied. highest was identified misfits within about 10\ifmmode^\circ\else\textdegree\fi{} deviation from perfect twin. These contain repeated building structure consisting typical $\ensuremath{\Sigma}=3$ symmetrical tilt twin highly disordered steps those units. other types misfit, also observe some coherence, accommodation occurs regular pattern. cases studied include high-index common axis show coherency that independent size. Similar results are obtained samples containing only boundaries, where arrays larger materials observed. provide evidence against view nanocrystals as disordered, amorphous, or liquidlike interfaces. suggest actually similar to polycrystals.