The Determination of Thermal Diffusivity of Aluminum Alloys at Various Temperatures by Means of a Moving Heat Source

Abstract

Abstract Previous work has demonstrated that the theory of moving heat sources can be used for a direct and rapid determination of thermal diffusivity in metals at high temperatures. Present work describes the experimental procedure and instrumentation which have been developed for metals of relatively high thermal diffusivity, 0.2 cm2/sec and more. The method was applied to two aluminum alloys, 3S and 61S which are commonly used for welding purposes. Therefore the results are believed to have practical significance. The thermal diffusivity of both alloys shows little or no increase with temperature from 150 to 1000 F. To check the reliability of results the thermal diffusivity of a sample of deoxidized copper was determined, first by this method, and then independently from its electrical resistivity using published data of the Franz-Wiedemann ratio for copper alloys. The two determinations agreed within ±1 per cent. The results on aluminum alloys proved that values of thermal diffusivity, averaged over an interval of 100 deg F, can be determined easily to three significant figures. The reproducibility of individual results was found to be largely independent of the velocity and intensity of the heat source and the wall thickness of the specimens. It was of the order of ±2 per cent. However, six consecutive runs can be made readily within two or three hours, thus reducing the probable error to a much lower value.