Analysis of interdiffusion of Dy, Nd, and Pr in Mg

The diffusion characteristics of Mg-rare-earth diffusion couples were studi ed. Cylinders of pure Mg and rare earth (Dy, Nd, and Pr) were abutted and a nnealed at 500 degreesC for 100 h or 300 h. Point-by-point composition prof iles were collected starting in pure Mg, across the diffusion zone, and end ing in the pure rare earth, using energy dispersive x-ray spectroscopy with a scanning electron microscope. The intermetallic phases that resulted due to diffusion were identified and compared to existing phase diagrams, for which the data is limited. For each diffusion couple, a plot of concentrati on versus distance perpendicular to the original plane of contact was obtai ned and analyzed using the Boltzman-Matano method. The interdiffusion coeff icients for each set of phases were then calculated. The results show that diffusion through the intermetallic phases is much slower than is expected in a solid solution.