Coarsening of polyhedral grains in a liquid matrix

The coarsening of polyhedral grains in a liquid matrix was calculated using crystal growth and dissolution equations used in crystal growth theories for faceted crystals. The coarsening behavior was principally governed by the relative value of the maximum driving force for growth (Delta g(max)), which is determined by the average size and size distribution, to the critical driving force for appreciable growth (Delta g(c)). When Delta g(max) was much larger than Delta g(c), pseudonormal grain coarsening occurred. With a reduction of Delta g(max) relative to Delta g(c), abnormal grain coarsening (AGC, when Delta g(max) >= Delta g(c)) and stagnant grain coarsening (SGC, when Delta g(max) < Delta g(c)) were predicted. The observed cyclic AGC and incubation for AGC in real systems with faceted grains were explained in terms of the relative value between Delta g(max) and Delta g(c). The effects of various processing and physical parameters, such as the initial grain size and distribution, the liquid volume fraction, step free energy, and temperature, were also evaluated. The calculated results were in good agreement with previous experimental observations.