Elastic and plastic aspects of martensitic transformations

Elastic and plastic aspects of martensitic transformations are discussed using the topological model. Here the interface comprises an array of transformation dislocations (disconnections) and dislocations (slip/twinning) superposed on coherently strained terraces. Plastic transformation strain arises by virtue of the conservative motion of the defect array, and is quantified directly in terms of the Burgers vectors of the defects. Superposition of the elastic fields of the defects and the coherency strain produces a short-range interfacial distortion field, but only rigid rotation, φ, of the phases at long-range. Furthermore, the treatment shows that, for elastically isotropic phases with similar moduli, elastic relaxations cause the habit plane to differ by φ/2 from the classical predictions where such relaxations are suppressed. A nonlinear analysis is presented suitable for instances of large values of φ. However, the plastic transformation strain, in combination with the relative orientation, φ, corresponds to the classically predicted shape deformation.