Single crystal growth of intermetallic compounds by a two-phase RF floating zone method

The radio frequency floating-zone growth of massive intermetallic single crystals very often fails due to an unfavourable solid-liquid interface geometry enclosing concave fringes. This interface depends on the flow in the molten zone. A tailored magnetic two-phase stirrer system has been developed enabling to control the melt flow ranging from intense inwards to outwards flows. Depending on the phase shift between the two induction coils, a transition from a double vortex structure to a single vortex structure is created at a preferable phase shift of 90°. This change in the flow field has a significant influence on the shape of the solid-liquid interface. The magnetic system was applied to the crystal growth of TiAl alloys. The segregation behaviour was studied and the experimental results were compared to samples grown with the common optical floating-zone technique.