Artikel

Phase Equilibria and Transformations - Presentation of various software approaches

The development and optimisation of new materials for applications under enhanced and complex service conditions require new instruments for the treatment of transformations. They have to be based on fundamental principles in order to provide predictability. Empirical approaches cannot meet these requirements.

In practice materials are multi-component systems. Their phase equilibria can only be obtained using numerical techniques. This gave rise to the computational thermodynamics which is based on a description of the thermodynamic functions by appropriate modelling. The parameters of these functions are obtained from experimental data by optimization methods. At present thermodynamic databases are available for various classes of materials representing a valuable tool for materials development and for the solution of complex technological problems. The calculation of stable and metastable phase equilibria as function of temperature and composition provides the basis for determining the effect of alloying elements on the precipitation behaviour. Chemical reactions can be calculated under various boundary conditions yielding the input for process simulation.

The computer simulation of phase transformations, based upon multi-component thermodynamics, offers an excellent tool for treating the kinetics of microstructure formation. This includes the morphological evolution during transitions, the prediction of precipitation sequences of stable and meta-stable phases and microstructural long term stability. Since data on true thermodynamic driving forces are provided by the thermodynamic software, the required kinetic data are reduced to the mobilities of the elements in the various structures. These are available for many substances and phases. At present there exist three different approaches focusing on different aspects: (a) the sharp interface concept with local equilibrium at the moving boundary (DICTRA), (b) the phase field method with a diffuse interface allowing for a treatment of morphological evolutions like dendritic solidification (MICRESS), (c) the meanfield treatment of multicomponent, multi-phase precipitation using the concept of maximum rate of entropy production (Onsager’s extremum principle), including finite interface mobilities and large deviations from local equilibrium (MatCalc).

It is the aim of this seminar:
• to present these approaches in detail
• to show their excellent predictive capability,
• to demonstrate how to work with the software. This will be done interactively by particular case studies.

The seminar addresses materials engineers and scientists in research and development departments in industry and at Universities.

Chairman of the seminar is Prof. Dr. G. Inden, retired from Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf.

Detailed information and registration is available at: http://dgm.de/fortbildung/?tgnr=1447&lg=en