The effect of energy conservation on the decomposition of unstable states is considered for systems undergoing a first-order phase transition with a nonconserved order parameter. Thermodynamic stability analysis shows that in a large enough initially supercooled adiabatic system the mixture of parent and product phases separated by a domain wall is preferred. However, in a small particle a homogeneous phase intermediate between the parent and product phase structures can form. Dynamic analysis of unstable phase decomposition identifies the thermodynamic and kinetic parameters defining different nonlinear dynamic regimes. This includes an interesting regime in which the order parameter is ''slaved'' to the local temperature. Further evolution of the system has been studied by one-dimensional numerical simulation which reveals three mechanisms of spontaneous domain formation: nonclassical nucleation, continuous modulation, and a hybrid mechanism. Formation of a domain structure is followed by stages of growth and coarsening. Growth can involve heat trapping by the product metastable phase, leading to a transient ''overshooting'' of the transformed fraction. Coarsening exhibits both coalescence and dissolution and follows a path of sequential period doubling. The results are discussed in terms of application to different first-order phase transformations, including ''quasimartensitic'' displacive transformation.
ASJC Scopus subject areas
- Statistical and Nonlinear Physics
- Statistics and Probability
- Condensed Matter Physics