

Thermal Conductivity in Comparison with Electrical Resistivity of Selected Alloys at Elevated Temperatures
Abstract
In contrast to pure metals, solid alloys at elevated temperature usually show significant deviations from the Wiedemann-Franz law (relating electrical resistivity to thermal conductivity) using the theoretical Lorenz number. This is due to the lattice component of the thermal conductivity and inelastic scattering by solute atoms, as well as other smaller contributions. Two experimentally determined constants can take into account these contributions (obtained by a Smith-Palmer-plot), re-establishing a welldefined relation between thermal and electrical conductivity. In this work, results of measurements of selected thermophysical properties of aluminum-, iron-, and nickel-alloys are reported. These are thermal diffusivity measured by the laser-flash method, heat capacity measured by differential scanning calorimetry, thermal expansion measured by push-rod dilatometry, and density at room temperature measured by an Archimedean balance. From these experimentally obtained data, thermal conductivity was calculated in a wide temperature range from room temperature to the melting region of each alloy. Electrical resistivity was measured in the same temperature range by a four point probe resistivity measurement using a millisecond pulse-heating technique. The measurement results of electrical resistivity as a function of specific enthalpy were combined with results of specific heat capacity measurements to obtain the relation between resistivity and temperature. From the results of thermal conductivity and electrical resistivity, the individual Smith-Palmer plots for the different alloys are obtained. Fitting the results to a linear function, the two constants are determined; these results are compared to values reported in literature.
DOI
10.12783/tc34-te22/36205
10.12783/tc34-te22/36205
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