Diffuse martensitic transitions and the plasticity of crystals with a shape memory effect

The mechanism of diffusion-free (thermoelastic) martensitic transitions in solids is theoretically examined using a thermodynamic approach together with a self-consistent-field order parameter model. Based on the resulting equations, a theory of smeared martensitic transitions is constructed as a kinetic equilibrium theory of heterophase structures which takes into account heterogeneous martensite nucleation and the interaction of interphase boundaries with various types of structural defects in real materials. An extensive comparison is made between the theoretical predictions and the experimental data on thermoelastic martensitic transformations in alloys with shape memory. The universal nature of the theory of diffuse first-order phase transitions is illustrated by applying it to ferroelectric and ferroelastic transitions in some classical ferroelectric and high-temperature superconductors.