Grain Boundaries in a 2-D Superlattice

In bicrystals with CSL orientation relationships two kinds of coincidence site lattices form, resulting in two kinds of grain boundaries. We examine the thermodynamic properties, using a lattice gas model, and make microstructural predictions about the dihedral angles at junctions between these boundaries. The behavior of these boundaries is examined for low temperatures and through the critical disordering temperature. Some aspects of nonstoichiometry are presented. A wetting transition is found at low temperatures, in which one kind of grain boundary is converted into the other by expelling antiphase domain boundary. No wetting transition is found at the critical temperature because an unusually high critical exponent of 3 is found for the difference in grain boundary energies between the symmetric and antisymmetric cases.