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 (δgmax), which is determined by the average size and size distribution, to the critical driving force for appreciable growth (δgc). When δg max was much larger than Agc, pseudonormal grain coarsening occurred. With a reduction of δgmax relative to δgc, abnormal grain coarsening (AGC, when δgmax ≥ Agc) and stagnant grain coarsening (SGC, when Agmax Agc) 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 Ag max and Agc. 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. © 2009 Materials Research Society.