Einfluss von Kreuzkorrelationen auf die Interdiffusion in aluminiumreichen Al-Ni-Schmelzen

To study the relation of self- and interdiffusion at low concentrations experimentally, interdiffusion in aluminum-rich Al-Ni melts are determined as a function of temperature and concentration. In order to prevent measurements to be disturbed by convection, a setup was used which combines the shear-cell method with X-ray radiography. This allows for time-resolved in-situ measurements with improved process control. Possible concentration-shifts during melting or solidification are avoided. Buoyancy-driven convection was excluded by experiments aboard the sounding rocket MAPHEUS-4. Cross correlations slow down interdiffusion considerably, as can be seen in combination with self-diffusion coefficients and the thermodynamic factor. This is the case even at concentrations as low as 2 at.\% Ni. Consequently Darken's equation is not valid in this case