Grain boundary junction engineering

Under certain circumstances grain growth in polycrystals is controlled by the mobility of grain boundary junctions. The resulting microstructure is distinctly different from the granular assembly in the course of normal grain growth. Also, the structure established under junction control is rather stable even under the conditions characteristic for grain growth governed by grain boundary motion. This provides a means of controlling the grain microstructure evolution, in particular of ultrafine grained and nanocrystalline materials. It is demonstrated that such an effect can be expected not only for 2D arrangements but for 3D microstructures with quadruple junctions as well. The latter statement is supported by an assessment of the mobility of quadruple junctions. We propose to introduce a new branch of grain boundary engineering, namely grain boundary junction engineering.