Deformation of polydomain crystals

Deformation of polydomain crystalline materials consisting of domains of di fferent phases or domains of differently oriented areas of the same phase a re considered. These polydomain materials are adaptive if their domain micr ostructure can change in response to a change of external mechanical or ele ctrical fields. For ferroelastic and martensitic transformations in shape m emory alloys the domain interfaces are so mobile that the deformation is al most reversible. Therefore, it can be treated as a superelastic deformation which is additional to the elastic one. Thermodynamic analysis of the evol ution of an equilibrium microstructure has shown that the mechanical behavi or of a transforming crystal is in principle different for displacement con trolled deformation and for load controlled deformation. The different type s of the microstructure are considered: (1) a heterophase polydomain; (2) a heterostructures containing besides an adaptive component, a passive compo nent which remains unchangeable during the deformation.