Convection and phase change in multi-component systems. Growth of Ga-Ge and Pb-30%Tl

The Bridgman technique is a directional solidification technique. The mater ial is loaded into an ampoule, and solidified by varying the temperature fi eld with a translation of the ampoule through a furnace. The hydrodynamic i s governed by both thermal and solutal convective instabilities. The resolu tion of the problem uses an homogenized formulation of the conservation equ ations, the enthalpy approach, issued from classical mixture theory. The nu merical simulation is done using a finite volume method. We present here st udies on two types of Bridgman configurations. The first one, corresponding to an inverse Bridgman configuration (heated from below), shows the intera ction between the interface and the hydrodynamic of the unsteady melt. The second one shows the solidification of a binary alloy in a normal Bridgman configuration, and shows the influence of thermo-solutal convection on the crystal constitution.