Thermophysical Data for the Development of Mathematical Models of Solidification

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Thermophysical data for liquid metals and alloys are very important as input data for mathematical models of solidification. The aim of this collaborative work is to develop methods for measuring thermal conductivities, specific heat capacities and emissivities for liquid metals and alloys.(A) Thermal conductivity measurementThe hot wire method has been improved : The hot wire probe should be coated with insulated substance to avoid current leakage when applied to conducting materials. The probe wires were made of alumel and oxidized thermally, which produced an insulated oxide film on the surface. The thermal conductivity value for mercury measured using this probe is 13W/mK,which is larger than the published value 8.5W/mK.This discrepancy would be due to convection, about which further work should be made. The use of Pt containing Al as probe wires is prospective for measuring on liquid metals at high temperatures.(B) Specific heat capacity measurementThe combination of the drop-calorimeter and levitation method has been proposed to avoid contamination from crucibles : A sample is melted and held at high temperature using the levitaion method and then dropped into a calorimeter. Further investigation is being made about the possibility of this method.(C) Emissivity measurementEmissivity has been measured by comparison between spectral intensities of a liquid sample radiation and of blackbody radiation. The emissivity values for liquid copper and nickel at the wavelength 800nm have been determined to be 0.10 at 1673K and 0.31 at 1873K,respectively. Measurements in infrared wavelengths are also required. The cold crucible technique would be helpful to avoid oxidation and contamination of samples.