The paper is concerned with a micro-mechanical model of stress-induced martensitic transformations in single crystals of shape memory alloys. In agreement with numerous experimental observations the transformation is assumed to proceed through the formation and growth of parallel martensitic plates within the austenite matrix. The phase transition takes place when the thermodynamic driving force at a phase transformation front reaches a threshold value. Macroscopic stress-strain relationships that correspond to pseudo-elastic behaviour are derived for evolving laminated microstructures, with full account for different elastic anisotropic properties of the product and parent phases. This difference in elastic properties leads to the redistribution of internal stresses during transformation which can affect the microstructure evolution. The class of analysed microstructures includes higher rank laminates. In particular, formation of internally twinned martensite plates is examined and the effect of detwinning through migration of interfaces between two martensite variants is modelled. In order to study size effects the model is extended by taking into account the interfacial energy. As an application of the model, the evolution of microstructure is studied for cubic-to-orthorhombic and cubic-to-monoclinic transformation in Cu-based shape memory alloys (CuAlNi and CuZnAl). Both the microstructure evolution and stress-strain diagrams are shown to depend on the orientation of the load axis with respect to the crystalline axes of the parent phase as well as on the sense of loading, i.e. tension or compression. Detwinning has been found to reduce significantly the effective tangent stiffness modulus of the twinned martensite. Macroscopically nonuniform transformation is predicted due to the softening behaviour at the material point scale.

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