Impurity diffusion coefficients of Al and Zn in Mg determined from solid-to-solid diffusion couples

Increasing use and development of lightweight Mg-alloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As property enhancing components, Al and Zn are two of the most important and common alloying elements for Mg-alloys. We have investigated the concentration dependent interdiffusion of Al and Zn in Mg using diffusion couples of pure polycrystalline Mg mated to Mg solid solutions containing either <9 at.% Al or <3 at.% Zn. Concentration profiles were determined by electron micro-probe microanalysis of the diffusion zone. The interdiffusion coefficients were determined by the classical Boltzmann-Matano method within the Mg solid solution. As the concentration of Al or Zn approaches the dilute ends, we employ an analytical approach based on the Hall method to estimate the impurity diffusion coefficients. Results of Al and Zn impurity diffusion in Mg are reported and compared to published impurity diffusion coefficients typically determined by thin film techniques.