Influence of Thermal Gravitational Convection on Solidi Fication Processes

Abstract

AbstractThe aim of these experiments in the Gradient Furnace with Quenching device (GFQ) during the German D-1 Mission was to study the influence of thermal convection on– the diffusion in the melt ahead of the solidification front in an AlCu-alloy– the stability of a smooth solidification front in an Al-Cualloy and– the morphology of the solidification front in an AlSi-alloyduring the directional solidification of the binary alloys AlCu with 0.3 wght.-% Cu and AlSi with 7.0 wght.-% Si. Altogether five samples had been successfully processed during the D1-Mission. After getting the complete values from the process data (above all the velocity of the solidification front and the temperature gradient) reference experiments were made in the same GFQ under lg-conditions.Additional experiments under lg with a transparent fluid were done to obtain information about the thermal convection in a cylindrical cell while measuring temperature distribution at the same time.A first result having the same crystallization condition is the more than twice thicker diffusion boundary layer in AlCu 0,3-specimen than in the lg-reference specimen. The diffusion coefficient and the dendritic morphology are to be determined. The evaluation of all specimens (flight- and lg-samples) is not finished in the moment.