The Influence of Solute Concentration on Impurity Diffusion in Magnesium Solid Solutions

Light-weight wrought magnesium alloyed with aluminum and zinc offer good room-temperature strength and ductility combined with corrosion resistance, weldability, and thermal and electrical conductivity. As a result, Mg-Al-Zn alloys can be found in aerospace applications such as aircraft fuselages, electronic housings, and EMI filters and shields. The present work examines the influence of solute concentration on impurity diffusion coefficients of Al and Zn in Mg(Zn) and Mg(Al) binary solid solutions, respectively. Experimental investigation was carried out with solid-to-solid diffusion couples of binary and ternary polycrystalline alloys. Concentration profiles were measured by electron microprobe micro-analysis and the impurity diffusion coefficients were determined by the Hall Method. Results of Al and Zn impurity diffusion in Mg solid solutions are reported and compared to respective impurity diffusion coefficients in pure Mg. Consistent with the findings of other researchers, Zn impurities diffuse faster than Al impurities in pure Mg and the Zn impurity diffusion coefficient is only slightly affected by the concentration of Al in Mg(Al) solid solutions. Unique to this study is the investigation of the diffusion behavior of Al impurities in Mg(Zn) solid solutions. The relationship of Al impurity diffusion with Zn concentration and temperature is discussed.