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

Grain growth in polycrystals is a process that occurs as a result of the 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-sided. A recent theory of 2-D grain growth is explicitly based on this fact, treating the switchings as random events. The process of shrinking of 4- and 5-sided two-dimensional grains was observed experimentally on polycrystalline films of transparent, pure succinonitrile (SCN). Grain shrinking was studied theoretically and simulated by computer (both dynamic and Monte Carlo). It was found that most shrinking grains are topologically stable and remain within their topological class until they are much smaller than their neighbors. We discuss differences which 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.