TOPOLOGICAL EVENTS IN 2-DIMENSIONAL GRAIN-GROWTH - EXPERIMENTS AND SIMULATIONS

Grain growth in polycrystals is a process that occurs as a result of t he vanishing of small grains. The mean topological class of vanishing two-dimensional (2-D) grains was found experimentally to be about 4.5. This result suggests that most vanishing grains are either 4- or 5-si ded. A recent theory of 2-D grain growth is explicitly based on this f act, treating the switchings as random events. The process of shrinkin g of 4- and 5-sided two-dimensional grains was observed experimentally on polycrystalline films of transparent, pure succinonitrile (SCN). G rain shrinking was studied theoretically and simulated by computer (bo th dynamic and Monte Carlo). It was found that most shrinking grains a re topologically stable and remain within their topological class unti l they are much smaller than their neighbors. We discuss differences w hich were found with respect to the behavior of 2-D polycrystals, a 2- D ideal soap froth, and a 2-D section of a 3-D grain structure.