The electrical resistivity during pre-precipitation processes

Abstract

The behaviour of the electrical resistivity of a binary alloy during preprecipitation is discussed on the basis of a model in which the conduction electrons are described by free wave-functions and are scattered by deviations from the average lattice potential due to localized atomic clustering. The maximum in the resistivity which appears during ageing is shown to occur when the linear dimensions of the clusters become comparable with the conduction electron mean free path length. Qualitative predictions are in agreement with the experimental observations in the cases of linear, platelet and spherical clusters, whether these are considered to arise from nucleation and growth processes or spinodal decomposition. The dependence of the resistivity on the decomposition wavelength is also discussed and the case of atomic short-range ordering (as distinct from clustering) is briefly considered. The lack of experimentally determined atomic correlation parameters, however, precludes any detailed quantitative comparison at this stage.