Transient eutectic solidification in In-Bi-Sn: Two-dimensional experiments and numerical simulation

A technique widely used for the in situ observation of microstructure formation in transparent organic systems was applied to metallic alloys with low melting temperature. In the ternary eutectic alloy system In-Bi-Sn, we observed by light microscopy steady state and transient eutectic microstructure formation during unidirectional solidification in thin (5-10 μm) glass capillaries. Starting from an equilibrated planar single-phase front in a slightly off-eutectic alloy we studied the dynamic processes like nucleation of univariant, and finally invariant ternary eutectic when the liquid transforms into three distinct solid phases. Numerical microstructure simulation was performed by applying a general multiphase and multi-component phase field model which couples directly to the complete thermodynamic dataset of the In-Bi-Sn alloy system. Via comparison of the experimental to the simulated data some thermo-physical values like diffusion coefficients and critical undercooling for nucleation have been evaluated.