Directional melting and solidification of gallium in a traveling magnetic field as a model experiment for silicon processes

• A new experimental setup for directional solidification processes has been developed.
• Methods for precise, up-scalable model experiments using gallium are proposed.
• A coupled unsteady 3D model of melt flow and phase interface is validated.
• Traveling magnetic fields can lead to complex 3D shapes of the melting interface.

Small-scale model experiments for directional solidification processes are performed using a gallium volume with a square horizontal cross-section and dimensions of 10×10×7.5 cm3. A heater at the top and a cooler at the bottom generate a vertical temperature gradient while an external coil system produces a traveling magnetic field (TMF) leading to Lorentz forces in the melt. The position and shape of the phase interface as well as the melt flow during melting and solidification processes are investigated both experimentally and with a coupled 3D numerical model. Uncertainty in various experimental parameters and appropriate methods of calibration are discussed to enable precise validation of numerical simulations. A distinct influence of the melt flow is observed, which results in a concave melting interface with an upward TMF and a convex shape with a downward TMF. In both cases, the corner region demonstrates local deflections in the opposite directions, which illustrates the challenge to obtain a smooth interface shape in silicon solidification processes. These processes can be further investigated using the validated 3D model. Additionally, direct transfer of the results between model experiments and silicon processes using scaling laws is discussed.