Modulation mechanism for first-order transformations with nonconserved order parameters

The effect of energy conservation on the decomposition dynamics of unstable states is considered for systems with nonconserved order parameters. We demonstrate that close to the critical point of instability the dynamics of the order parameter field is described by the nonlinear Cahn-Hilliard equation, leading to microstructure evolution by heat-transfer-controlled modulation. The results are applied to first-order displacive transitions, predicting an alternative transformation mechanism that follows a path of continuous strain modulation with finite wavelength.