A theory of spinodal decomposition stabilized by coherent strain in binary alloys

A phenomenological theory is developed which predicts the possible existence of meta-stable chemical composition modulations in the spinodal (instable) region of the phase diagram of binary alloys. This is accomplished through a modified elastic energy term in the theory of diffuse interfaces by Cahn and Hilliard: Analogously to Cahn’s expansion of the molar chemical free energy, also the (un-relaxed) internal stress tensor due to chemical composition modulations is expanded in a Taylor series of the spatial derivatives of the local composition up to second order terms. This mathematical approach is confirmed by atomistic modeling.