Thermal conductivity of metals and alloys

The theory of the thermal conductivity of metals and alloys is reviewed. There are two components: electronic and lattice. The electronic component is related to the electrical conductivity by the Lorenz ratio. Deviations from the Sommerfeld value of the Lorentz ratio are discussed. At high temperature deviations are due to incomplete degeneracy of the electron gas (Fermi smearing), at low temperatures deviations are due to the inelastic nature of the electron-phonon interactions and to the electron-electron interactions. The lattice conductivity is discussed as a function of temperature, point defects, and electron density. The predictions of the theory are compared with measured thermal conductivities. For the elements, the effects of the lattice component can be distinguished from deviations of the electronic component from the Lorenz ratio. Three representative alloy systems are discussed. In aluminium alloys the lattice component is small, and the electronic component well behaved. In titanium alloys the lattice component is relatively larger, and limited both by point defects and by phonon-electron interactions. In face-centred iron-chromium-nickel alloys, the lattice component is significant, because the electronic component is small due to the solute atoms: point defects have little effect on the lattice component in most of these alloys.