Impurity And Tracer Diffusion Studies In Magnesium And Its Alloys

An Integrated Computational Materials Engineering (ICME) approach for optimizing processing routes for Mg-alloys requires reliable thermodynamic and diffusion databases. We are developing an impurity and tracer diffusion database using both stable and unstable isotopes for Mg and its alloys. In this study, Al impurity diffusion in pure polycrystalline Mg (99.9%) was examined using the thin film method. Approximately 500 nm thick Al films were deposited on in-situ RF plasma-cleaned polycrystalline Mg by DC magnetron sputtering from pure Al (99.9%) targets. Specimens were then diffusion annealed at 300 and 400°C in quartz capsules that were evacuated to 10-8 torr and backfilled with Ar-H2 mixtures. Concentration profile of Al diffusion profiles into single phase Mg was determined by depth-profiling technique using secondary ion mass spectroscopy. The Al impurity diffusion coefficients were determined at 300 and 400°C as 1.74 (±0.4) x 10-17 m2/sec and 2.38 (±1.0) x 10-15 m2/sec, respectively