Interface Crystallography and structure in LaB6-ZrB2 directionally solidified eutectics

Interfaces in LaB6-ZrB2 composites directionally solidified by a zone melting process were characterized by transmission electron microscopy (TEM). The nominal crystallographic orientation relationship between the two phases corresponded to a high-symmetry near-coincidence site lattice (NCSL). The small mistilt (2 degrees-5 degrees) from the high-symmetry orientation relationship was shown to result in an increased volume density of coincident sites. Furthermore, the dominant interface facet planes were predicted by the NCSL model. The configurations of interfacial misfit dislocations were analyzed by high-resolution TEM and showed a good agreement with predictions based on the displacement shift complete lattice and secondary original lattice (O2-lattice) models. These analyses suggested that interfaces were relaxed to relatively low-energy configurations.