Heat transfer within a melt pool can have a strong effect on an evolving microstructure in parts produced through both conventional casting techniques and laser-based additive manufacturing methods. However, the heat capacity and thermal conductivity of metallic melts are challenging to directly measure due to the high temperature and high reactivity of the molten metal. Induction modulation calorimetry is a non-contact processing technique in which the input power into a sample is modulated and the thermal response of the sample is analyzed to determine the heat capacity and thermal conductivity of the material. This power modulation is accomplished in microgravity electromagnetic levitation by varying the electromagnetic field to induce variations in the power input into the sample. The distribution of volumetric heating is concentrated within the skin depth of the sample where the magnetic field is largest. Prior work has used a coupled reservoir heat flow model to describe the thermal response while accounting for both the volume directly heated by joule heating and the volume heated only by conduction [1].  For metallic melts of low viscosities, heat flow within the sample is driven not only by thermal conduction within the melt but also by forced convection due to the magnetohydrodynamic flow. The forced convection accelerates the distribution of heat throughout the molten sample and increases the relaxation rate of thermal gradients within the sample. Recent advances in multiphysics models have incorporated the magnetohydrodynamics, fluid flow, and heat transfer to determine the distribution of temperature within the melt. Current work is reevaluating data in the NASA-PSI system taken during the MSL-1 campaign to improve the accuracy of the measured thermal conductivity in various materials with upcoming work to apply this technique to measurements taken in the International Space Station Electromagnetic Levitation Facility.
[1] R. K. Wunderlich and H.-J. Fecht, “Modulated electromagnetic induction calorimetry of reactive metallic liquids,” Meas. Sci. Technol., vol. 16, no. 2, pp. 402–416, Feb. 2005, doi: 10.1088/0957-0233/16/2/011.