Measurement of thermophysical properties of metallic melts for high quality castings

The thermophysical properties of interest for casting simulations are melting range, fraction solid, density (thermal expansion), viscosity, specific heat, Gibbs free enthalpies, diffusion coefficients, thermal (electrical) conductivity, surface tension and emissivity. Some of these data can be obtained more or less accurately by conventional methods. High precision measurements on chemically highly reactive melts and fluids at the temperatures of interest require the application of containerless processing using non-contact diagnostic tools. By eliminating the contact between the melt and a crucible accurate surface nucleation control and the synthesis of materials free of surface contamination become possible. Under microgravity conditions, further advantages are expected from the significantly smaller electromagnetic fields needed to stabilize the containerless melts. This was shown in several Spacelab missions in which the results clearly showed an improvement in accuracy over terrestrial measurement, even on pure metals. This is an indication that the electromagnetic levitation technique provides a suitable environment for the accurate measurement of the thermophysical properties of metallic melts of industrial interest also on the ISS. The expected outcomings from a running “Thematic Network” funded by the European Commission and industry together with the new co-operative project “Thermolab” supported by industry and the European Space Agency within the frame of the ESA-Microgravity Applications Promotion program will allow a broader use of castings in different applications. Another RTD-project dealing with improved metal cast processing routes prepared for submittance to the EC this year will be clustered with other R&D-projects building up a “Virtual Institute for Advanced Casting.” The whole R&D-network will combine research activities of about 30 partners from 10 different european countries, where microgravity research and technology development activities are embedded in a large cooperative earth-bound research project.