Diffusion in multicomponent systems

First an overview on the diffusive fluxes of several components in a multicomponent system is presented. Also diverse reference system established in the literature are discussed. Flux balances are derived in the bulk of a material including vacancies. Their role is discussed in a detail with respect to their production and annihilation. Furthermore, evolution laws for the fluxes are derived by application of Onsager's principle of maximum dissipation rate. Both the flux balances and their evolution laws can be considered as physically based general versions of the classical 'laws' of diffusion. In addition balance relations at interfaces are explained. This allows finally to derive the thermodynamical driving force in a material point. Also in this case the role of vacancies is taken into account considering interfaces as ideal sources and sinks of vacancies. Finally, examples from solid/solid phase transformation in metals are demonstrated. It is emphasized that the concept presented is by no means restricted to metals.

Speaker: F.D. Fischer:
1 Institute of Mechanics, Montanuniversität Leoben
2 Erich Schmid Institute for Materials Science, Austrian Academy of Sciences, Leoben
3 Materials Center Leoben
4 Christian Doppler Laboratory of Functionally Oriented Materials Design