Modeling of eutectic growth kinetics with thermodynamic couplings

An original model of directional eutectic growth for lamellar eutectics is presented. This model is based on the analysis of thermodynamic equilibrium at the solidification front. Contrary to previous ones, this model does not use linearization hypothesis on the alloy phase diagram and takes into account variations of densities between phases. Moreover, curvature effects are considered on thermodynamic equilibrium at the solidification front. Its numerical implementation is made possible through a coupling with thermodynamic software based on the CALPHAD approach. This new numerical model is applied to the Al-Al₂Cu eutectic structure and compared to the Jackson-Hunt theory. Large differences between results of the present model and this theory are observed at high growth rate. In particular, curvature effects on phases concentrations can no more be modeled using a linear approximation, as in the Gibbs-Thomson relation. A good agreement of the numerical model with reported experimental studies is observed for a large range of growth velocities.