The effect of plastic deformation on the lattice thermal conductivity of alloys

• Main Author: Salter, J. A. M.
• Published: University of Surrey 1966
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.751663

The thermal conductivity of a series of alpha-phase copper aluminium alloys has been measured between 1.5 and 4.2 K. Lattice thermal conductivities have been deduced by assuming the validity of the Wiedemann-Franz law. The results for the annealed specimens have been compared with the kinetic model of lattice conductivity using Callaway's theory and phonon mean free paths derived from Pippard's theory of ultrasonic attenuation. It is shown that by a choice of mean free path consistent with the absence of any detectable cubic term in temperature in the lattice conductivity, the qualitative agreement between theory and experiment is good. Comparison of the thermal conductivities of annealed polycrystals and single crystals indicates the existence of a small negative linear term in temperature due to boundary scattering. Polycrystalline specimens were deformed in tension, and the resulting increases in lattice thermal resistivity measured. The dislocation densities introduced were measured by transmission electron microscopy, and the thermal resistivity per unit dislocation density obtained. The magnitudes for the latter are 2 to 6 times as great as those obtained experimentally for alpha-brass by Kemp et al. and Lomer and Rosenberg, and 15 to 50 times as great as the values obtained theoretically for pure copper by Klemens and Bross and Seeger; moreover, an apparent variation in dislocation phonon scattering power with aluminium content is observed. The possibility that this is due to dislocation pile-ups is considered.