ABSTRACT
Thus far we have shown that the mechanism of transport influences the rate at which the atomic, or molecular, constituents migrate throughout materials at a given temperature. In multicomponent systems, thermodynamic driving forces may exert a strong influence on the migration process and determine the spatial organization of the material constituents (Chapters 9 and 10; cf. Eq. 10.19). Specifically, thermodynamic forces induce the constituents of a homogeneous, concentrated, A/B mixture to demix and to self-organize and form spinodal patterns. Mechanistically, fluctuations of the local composition of an otherwise homogeneous mixture, residing in the unstable region of the phase diagram, may become amplified, forcing the mixture to phase separate into A-rich and B-rich phases. This phenomenon, spinodal decomposition, is ubiquitous and is exhibited by a diverse range of mixtures, from metallic systems and polymeric melts to network glass melts. The demixing is an illustration of microstructural development in an alloy, engendered by a thermodynamic driving force. This instability is one of a number of instabilities that occur in condensed matter and is of practical and scientific interest.
