What Can the Concept of a Perfect Chemoelastic Solid Tell us about the Mechanical and Thermodynamic Behaviour of a Solid ?

Abstract

The elastic energy stored in a solid is typically small compared to the energy involved in a phase change. As a consequence, it is relatively easy to generate elastic stresses by a modification of the composition and/or a phase transformation. Conversely, the influence of stresses on phase changes is only of importance in special situations. What kind of effects can we expect and what are the order of magnitude of the phenomena is the question which is addressed in this communication. Using a model of a perfect chemoelastic crystalline solid, developed in collaboration with J.W. Cahn many years ago, the various facets of the interactions between stresses and thermodynamics are reviewed. Besides a purely energetic action, the long range nature of the elastic forces and their anisotropy have unusual consequences for the material scientist. Thus because the global elastic energy in a self-stressed system undergoing a phase change is shape dependant, there is a coupling between elastic and surface effects, both contributing to the evolution of the shape of precipitates. The thin film geometry is very useful for the exploration of the new phenomena induced on equilibrium and kinetic evolution of multiphase solids by the presence of such stresses. Limitations of this model due to interactions with cracks or dislocations are briefly discussed.