Microstructural evolution in two-dimensional two-phase polycrystals

In two-dimensional polycrystals composed of α-phase and β-phase grains the stability of ααα, βββ, ααβ and αββ three-grain junctions and αβαβ four-grain junctions depends on the α-α, β-β and α-β interfacial energies. A computer simulation which generates thermodynamically consistent microstructures for arbitrary interfacial energies has been utilized to investigate microstructural evolution in such polycrystals when phase volume is not conserved. Since grain shapes, phase volume, and phase arrangements are dictated by interfacial energies, clustered-, alternating-, isolated-, and single-phase microstructures occur in different interfacial energy regimes. Despite great differences in microstructure, polycrystals which contain only three-grain junctions evolve with normal grain growth kinetics. In contrast, structures containing flexible four-grain junctions eventually stop evolving. We conclude that two-dimensional polycrystals continually evolve when grain junction angles are thermodynamically fixed, while grain growth ultimately ceases when grain junction angles may vary. Predictions concerning three-dimensional and phase-volume conserved systems are made.