Tracer diffusion in Pt3Fe ordered alloys

Tracer diffusion coefficients of Fe and Pd in L1(2)-Pt3Fe ordered alloys have been measured in the temperature range between 1223 K and 1663 K, which is through the order-disorder transformation temperature. The diffusion coefficient of Fe, D-Fe(*), increases with increasing Fe composition, while that of Pd, D-Pd(*), is almost independent of the composition. Both diffusion coefficients obey the Arrhenius law at temperatures up to 1374 K, while in the higher temperature range approaching the order-disorder transformation temperature, they show upward curvature. In the higher temperature range it has also been observed that the diffusion coefficient of Fe is larger than that of Pd, which is opposite to the diffusion behavior at lower temperatures. Using defect concentrations calculated by the thermodynamic model, the diffusion behavior in Pt3Fe ordered alloys can be understood within the framework of the alpha sublattice vacancy mechanism.