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Containerless experimental techniques to obtain thermophysical properties of liquid metals and alloys at high temperatures and density data for liquid aluminium

Abstract : High temperature experimentation with solid and especially liquid specimens faces numerous difficulties. Traditional static steady state techniques for the measurement of thermophysical properties are generally limited to temperatures of about 2300 K. This limitation is a result of chemical interaction of the specimens with the containers, the loss of mechanical strength, problems with heat transfer, evaporation and electrical insulation while the sample and its environment are kept for times up to hours at high temperatures. Containerless investigation methods have been developed to avoid these difficulties and to permit the extension of the measurements to higher temperatures. The methods used by our workgroup are on the one hand ohmic pulse heating and on the other hand an electromagnetic levitation technique both can be called containerless techniques. Pulse heating delivers thermophysical properties of electrically conducting materials far into the liquid phase. The measurements allow the calculation of specific heat capacity and the temperature dependencies of electrical resistivity, enthalpy and density of the samples at the end of the solid phase and in the liquid phase. Measurements of normal spectral emissivity at 684.5 nm increase the accuracy of the pyrometric temperature measurements. Thermal conductivity and thermal diffusivity as a function of temperature are estimated from resistivity data using the Wiedemann-Franz-law. Electromagnetic levitation, as the second experimental approach used, delivers data for surface tension (which is not available by means of pulse heating technique) and for density of liquid metals as a function of temperature. Properties of matter at high temperatures are useful for high-temperature technologies such as aerospace, nuclear energy and the establishment of temperature reference points, including applications which are subjected to high temperature - high pressure conditions, as well as input data for modeling, which got very popular recently in steel working industry to simulate casting and welding processes and in jewelry industry to reduce reject due to defects.
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  • HAL Id : hal-01335586, version 1

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G Pottlacher, K Aziz, A Schmon. Containerless experimental techniques to obtain thermophysical properties of liquid metals and alloys at high temperatures and density data for liquid aluminium. 8th International Conference on Electromagnetic Processing of Materials, Oct 2015, Cannes, France. ⟨hal-01335586⟩

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