PHASE-FIELD METHOD COUPLED TO CALPHAD: QUANTITATIVE COMPARISON BETWEEN SIMULATION AND EXPERIMENTS IN TERNARY EUTECTIC IN-BI-SN

摘要

While thermodynamic data have been successfully assessed for an increasing number of alloy systems from equilibrium experiments using the CALPHAD approach, there is still a tremendous lack of melt diffusion and surface energy data, which are needed for simulation of solidification processes.rnIn this paper we present an approach for determining liquid diffusion and surface energy data by comparing transient solidification processes and phase-field calculations. Solidification experiments in quasi-2D glass capillaries have been performed for the In-Bi-Sn system, where directional eutectic solidification was observed, beginning with the BiIn_2 primary phase and following various monovariant grooves before reaching the ternary eutectic. During the experiment, the exact front position vs. time was measured using an optical CCD camera. Simulation was done using a multi-phase-field model, coupled online to an optimized thermodynamic database for In-Bi-Sn. By applying systematic variations to the unknown parameters in several simulation runs, it was possible to determine the liquid diffusion coefficients and critical nucleation undercooling by direct comparison to the corresponding experiments. This method shows an alternative way of obtaining thermophysical data with the aid of numerical simulation.