Heat Conduction in Alloys at Low Temperatures

With a view to studying the mechanism of heat conduction in low conductivity alloys, a method has been devised by which the thermal conductivity of relatively small samples (⅛- to ¼-inch diameter, 1 to 2 inches long) of various materials can be measured in the temperature regions obtainable with liquid nitrogen, liquid hydrogen, and liquid helium. Preliminary measurements on several commercial alloys (monel, inconel, and stainless steel) gave Wiedemann-Franz ratios several times greater than the theoretical value of 2.45×10−8 watt-ohm/deg2, the deviation being greater for annealed than for cold-worked specimens. This has been interpreted in terms of appreciable lattice conduction of heat in these alloys. Following these results, samples of an alloy of 90 percent copper 10 percent nickel were prepared with varying amounts of cold-work and with different grain sizes. Results with these samples were similar to those obtained with monel and inconel and confirm the hypothesis of lattice conduction. They also give a qualitative indication of the effectiveness of cold-work in limiting the lattice conduction of heat.