High-Temperature Electric and Thermal Conductivity of the Aluminum Alloys SAV-1 and AMG-2

Abstract

The electric and thermal conductivity of the aluminum alloys AMG-2 and SAV-1, which are used to fabricate the fuel elements of the fuel assemblies of a nuclear reactor, was investigated in the range 290‐490 K. The Debye temperature was calculated and the contribution of the electronic and lattice components to the thermal conductivity of the alloys was determined. It is shown on the basis of an analysis of the mechanisms of electron and phonon scattering and the experimental data that one possible reason for the observed changes of the thermal conductivity in aluminum alloys are the scattering of electrons by phonons and the deviation of the Lorenz number from the theoretical values as a result of inelastic scattering of the electrons. Aluminum alloys distinguished by their physical properties, viz., strength, high plasticity, corrosion resistance, and large store of plasticity, are widely used as a structural material in nuclear reactors of different types. AMG-2 and SAV-1 belong to the group of deformable aluminum alloys in the ternary system Al‐Mg‐Si. Their physical properties depend largely on the ratios of the concentrations of aluminum and the main alloying elements ‐ magnesium and silicon. In addition, different intermellide compounds, for example, AlSiMnFe, AlSiFe, CuAl 2 , and others, can be present in such alloys [1]. The high thermal conductivity and weak susceptibility to radiation damage make it possible to operate a structure based on them in the presence of significant thermal loads, specifically, fabricate protective cladding of fuel elements and different structures in the reactor core that operate in a wide range of radiation fields [2]. All this generates interest in studying these materials. In [3], low-angle neutron scattering was used to study the superatomic structure and it was shown that pores with characteristic radius 5‐50 nm are present in samples of the alloy SAV-1. It was found that irradiation causes an appreciable reduction of the volume fraction of the large scattering structure with radius 40‐50 nm and together with this an increase of the relative amount of the fractions with radius less than 20 nm. The results of neutron studies are correlated with mechanical tests of irradiated alloys and changes in their elemental composition [4]. At the same time the thermal and electrical characteristics of the alloys have not been adequately studied. The thermal conductivity of the alloy SV-1 and its temperature dependence were studied in [5]. However, because there are no data on the electric conductivity the conclusion concerning the relative contribution of possible mechanisms of heat transfer in the experimental temperature range was an estimate. In this connection, in the present work the temperature dependence of the electrical conductivity and the thermal conductivity of the related alloys SAV-1 and AMG-2 were studied in order to obtain a more accurate description of the physical properties of aluminum alloys.