Thermophys.Properties of Alloys in the Solidification Range

Thermophysical properties, which are input parameters in the computer simulation of technical processing of metallic materials, were measured. The obtained results lead to a significant improvement in the numeric modeling of production processes. A millisecond pulse-heating system was developed at the Austrian Foundry Research Institute to determine very accurately thermophysical properties of metals at high temperatures. By passage of a high electrical current, specimens are heated within several hundred milliseconds up to the melting range. The imparted energy and the electrical resistivity is obtained by the time-resolved measurement of current and voltage drop along a defined portion of the specimen. During the experiment, temperature of the specimen is measured by a fast pyrometer. From this measurement, enthalpy as a function of temperature (heat capacity) is obtained. Due to the short duration of the experiment, heat transport by thermal diffusion is negligible, the (small) heat loss by radiation is considered by measuring it in the cooling phase. The electrical resistivity as a function of temperature is calculated by Ohm`s law, and, for metallic materials, this property is closely related to thermal conductivity (Wiedemann-Franz law). Additionally, thermal expansion as a function of temperature was measured very precisely by a double Michelson interferometer. The thermophysical properties obtained at the Austrian Foundry Research Institute are accessible to interested industries. The topic has become even more relevant, since several Austrian companies have themselves begun to perform numerical process simulation. The Austrian Foundry Research Institute itself benefits from the acquired data, since the quality of the fluid flow and solidification simulation service was further improved.