Coherency and loss of coherency in lamellar Ti---Al

A grain of fully lamellar Ti---Al is modeled as a periodic multilayer which may contain any number of layers, each with different lattice parameters, different (isotropic) elastic constants and different thicknesses. Formulae are given for the coherence (plane) stress and strain tensors in any layer. The γ layers all have inplane shears and a biaxial tension whereas the ₂ layers have principally a biaxial compression. The coherence stresses expected in various forms of fully coherent Ti---Al are tabulated. Estimates are made of the lamellar thicknesses at which the material becomes semi- or partially- coherent and of the residual coherence stresses in these materials.