Thermodynamic modeling and diffusion kinetic experiments of binary Mg–Gd and Mg–Y systems

Diffusion couple experiments for the Mg–Gd and Mg–Y systems were performed with Mg single crystals to investigate the anisotropic diffusion behavior of Gd and Y in hexagonal close packed (hcp) Mg at temperatures between 703 and 803 K (430 and 530 °C). Diffusion coefficients for both Gd and Y along the basal plane of hcp Mg are approximately three times higher than those along the normal direction of the basal plane. The impurity diffusion coefficients of both Gd and Y in hcp Mg are lower than the self-diffusion of Mg and impurity diffusions of Al and Zn by about one order of magnitude. Growth constants and inter-diffusion coefficients of the intermediate phases for both systems were determined. Accurate thermodynamic modeling of the Mg–Y and Mg–Gd systems were also carried out based on the phase diagram data obtained from the present diffusion couple experiments and available literature data.