The effect of elastic energy upon the anisotropy of the antiphase boundary interfacial energy was studied theoretically. The model treated the composition and atomic ordering as local variables which were defined on each of the atomic planes parallel to the antiphase boundary. The equilibrium structure was found in terms of a set of planar variables that minimized the free energy. A strain energy term, which involved an orientation-dependent stiffness parameter and a phenomenological law which gave the lattice constant as a function of the local composition and order parameter, was included in the definition of the free energy. Elastic effects in the antiphase boundaries of B2 ordered alloys with an Al atomic fraction of 0.2 to 0.3 were investigated. It was found that, in spite of the high elastic anisotropy of the alloys, elastic effects were not expected to result in any appreciable anisotropy of the antiphase boundary interfacial energy. This was so because, in these alloys, the variation in lattice constant that was due to order parameter variation at the antiphase boundary was almost completely cancelled out by the variation in lattice constant that was due to compositional variations. In a theoretical model, using physically reasonable parameters, the antiphase boundary energies were found to vary by up to 9% as a function of orientation. This was due only to elastic effects. It was concluded that an elastically introduced antiphase boundary anisotropy would be observable in alloys such as Fe-Si, where lattice constant variations due to order parameter variations cooperated with those that were due to compositional variation.

R.G.Van der Heide, S.M.Allen: Acta Materialia, 1999, 44[4], 1613-21