Role of grain rotation during grain growth in a columnar microstructure by mesoscale simulation

We use a mesoscopic simulation approach to study the coupling and competition between grain-boundary-curvature driven and grain-rotation-coalescence induced grain growth in a <001> textured columnar microstructure. The well-known variational formulation for the total dissipated power, due to Needleman and Rice, provides the formal basis for our two-dimensional simulations. A stochastic velocity Monte-Carlo algorithm is used to minimize the functional in each time step. The competition between grain-boundary migration and grain rotation introduces a physical length scale, R-c, into the system, enabling the growth process to be characterized by two regimes. If the average grain size is smaller than R-c, as is the case in nanocrystalline materials, grain growth is dominated by the grain-rotation-coalescence mechanism. By contrast. if the average grain size is greater than R-c, then growth is dominated by curvature-driven grain-boundary migration. The growth exponents characterizing the power-law time dependence of the average grain size are different for the two growth regimes. An extended von Neumann-Mullins relation, based on averaged grain-boundary properties, is further extended to include the effect of grain rotations. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.