Diffusionsmessungen in aluminiumreichen Aluminium-Germanium-Schmelzen

Abstract

The aim of this study was to determine the interdiffusion coefficients of Al-Ge alloys and to analyse their temperature and concentration dependence. Six experiments with three interdiffusion couples each were planned at 973, 1073, and 1173 K, covering mean compositions of 10, 17.25, 25, 40, 45.8, and 51.6 wt.% Ge. The experiments were conducted using the shear-cell method with continuous in-situ X-ray monitoring. The evaluation followed the Common-Erf model. Concentration profiles were represented as step-like functions of position, and the resulting diffusion coefficients were plotted as a function of time. The slope of the regression line corresponded to the mean diffusion coefficient of each composition. Due to complications, only four of the six experiments were successfully completed. For temperature dependence, only a slight increase in the diffusion coefficients with rising temperature was observed, though the results correlated with predictions from the Darken equation. For concentration dependence, the diffusion coefficient decreased up to an atomic fraction of about 20% Ge, followed by an increase at higher contents, reaching their maximum at the highest concentration investigated. To draw reliable conclusions across a broader range, the two missing experiments with 40, 45.8, and 51.6 wt.% Ge at 1073 and 1173 K are essential.