Interdiffusion in the Al–Mg System

Interdiffusion in the aluminum-magnesium system was investigated in the temperature range of 325 to 425°C with diffusion couples of pure aluminum and magnesium.Electron probe micro-line analysis of specimens indicated that two intermediate phases, namely β and γ, were formed in the diffusion zone. It is concluded that the growth of each phase is controlled by the process of volume diffusion since the rate of layer growth obeys the parabolic law.The activation energies for the interdiffusion in β and γ phases estimated from the temperature dependence of the interdiffusion coefficients calculated by Heumann’s method were 13.6 and 28.1 kcal/mol, respectively.The Kirkendall effect was measured with a marker. The marker shifted to the aluminum side with respect to Matano’s interface. The result is opposed to that reported by Heumann and Kottmann who stated on the basis of Bungardt’s experimental study that the initial interface moves to the magnesium side with respect to Matano’s interface. The measurement of the Kirkendall effect showed that the diffusion in this system was controlled by a vacancy mechanism and that aluminum diffuses more rapidly than magnesium.