Three-dimensional simulations of microstructural evolution in polycrystalline dual-phase materials with constant volume fractions

The microstructural evolution of a polycrystalline dual-phase material with a constant volume fraction of the phases was investigated using large-scale three-dimensional phase-field simulations. All materials parameters are taken to be isotropic, and microstructures with volume fractions of 50/50 and 40/60 were examined. After an initial transient, the number of grains decrease from ∼2600 to ∼500. It was found that the mean grain size of grains of both phases obeyed a power law with an exponent of 3, and the microstructural evolution was found to be controlled by diffusion. Steady-state distributions of grain sizes and topology were determined. It was found that the grain size distributions were in good agreement with experimentally characterized size distributions for solid particles coarsening in a liquid matrix, and that the distributions of the number of faces were in good agreement with the topology of single-phase grain structures as determined by experiment and simulation. The evolution of size and number of faces for the minority and majority phase grains in the 40/60 volume fraction simulation is presented and discussed. Non-constant curvature across some interphase boundaries was observed, even though the interfacial energies are isotropic.