Aluminum Impurity Diffusion in Magnesium

The diffusion of Al in polycrystalline Mg (99.9%) was studied via depth profiling with secondary ion mass spectrometry in the temperature range of 573-673 K, utilizing the thin film method and thin film solution to the diffusion equation. Multiple samples with multiple depth profiles on each sample were obtained to determine statistically confident coefficients with a maximum standard deviation between measurements of 16%. The activation energy and pre-exponential factor of Al impurity diffusion in Mg were determined as 155 kJ/mole and 3.9 x 10(-3) m(2)/s, respectively. The Mg substrates have a small grain size (similar to 10 mu m) and therefore some contributions from grain boundary diffusion are expected in the measurements. Sputter roughening during depth profiling, which is inherent to the SIMS process, also contributes to the measured diffusion coefficient, especially in samples with smaller grain sizes.