Effect of rotational vibrations on directional solidification of high-temperature binary SiGe alloys

Abstract

Numerical investigation of flows and heat and mass transfer during the directional solidification of high temperature SiGe alloys in the presence of rotational vibrations has been performed. It has been shown that the structure of a vibration-induced flow has the form of a vortex localized near the crystallization front and the direction of this flow is such that the fluid moves along the front from the symmetry axis to the wall of the crucible. With the increase of the vibration parameter the intensity of the vortex grows, and the concentration gradient on the crystallization front near the crucible wall increases. This causes an increase in the crystallization temperature in this region, the temperature of the melt in this area becomes lower compared to the crystallization temperature, and hence the melt becomes overcooled. For the germanium-silicon system, changes in the gravity force lead to the changes in the flow and heat and mass transfer regimes, which are accompanied by a hysteresis. The analysis of the obtained numerical results has revealed that rotational vibrations are responsible for the disappearance of the zone of non-uniqueness.