Theory of rubber-like elasticity in shape memory alloys

We formulate a theory of the rubber-like behavior in shape memory alloys. The kinetics of the martensitic transformation is represented in terms of the local strain field. This primary order parameter is coupled with a secondary variable which follows the evolution of the order parameter but is assumed to be an extremely slow variable. From this set of equations, we derive the equation of motion for a twin boundary. The stress–strain relation due to the motion of twin boundaries is obtained by taking account of the aging effect. The results are found to be consistent, at least qualitatively, with experiments. The stabilization of the martensitic phase by aging is also argued.