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 titaniu...

Thermal conductivity of metals and alloys

For stainless steels 304, 310, and 316, longitudinal and transverse ultrasonic velocities were measured by a pulse‐echo method between 295 and 4 K. From these velocities were computed five elastic constants: longitudinal modulus, shear modulus, Young’s modulus, bulk modulus, and Poisson’s ratio. All three steels show low‐temperature elastic‐constant anomalies, which arise from magnetic phase transitions.

Stainless‐steel elastic constants at low temperatures

Thermal expansion and heat capacity of some stainless steels and FeNi alloys

The specific heat of fifteen stainless steels in the temperature range 4K-30K

Low temperature magnetic susceptibility and magnetization studies of some commercial austenitic stainless steels

Some magnetic and thermal properties of a stainless steel (AISI 310S) and an Inconel superalloy (X750) have been measured at cryogenic temperatures, and in most cases up to room temperature. The physical-property determinations were undertaken as part of a comprehensive investigation of the engineering properties of cryogenic structural materials applicable to superconducting machinery, i.e., machinery incorporating superconductive components. The alloys, whose properties are to be discussed here, were selected as candidates for advanced superconducting generator applications. Indeed, they have already been used in the construction of certain components of an experimental alternator currently under development. The alloys discussed below are categorized in terms of various melting practices and heat treatments with the codes corresponding to these conditions being defined in Table I. Further details regarding the procurement and metallurgical properties of these alloys are available elsewhere [1].

M. P. Mathur

Papers

Magnetic and Thermal Properties of Stainless Steel and Inconel at Cryogenic Temperatures