Self- and Impurity Diffusion in γ-TiAl Single Crystals

The diffusion coefficients of 44Ti, 63Ni and 59Fe in γ-TiAl single crystals have been measured by ion-beam sputter-sectioning technique, while those of In have been measured using ion implantation technique and secondary ion mass spectroscopy (SIMS) in order to clarify the diffusion anisotropy: the diffusion perpendicular and parallel to the [001] axis. The diffusion of Ti and In perpendicular to the [001] axis is faster than that parallel to the [001] axis. However, the diffusion anisotropies of Fe and Ni show opposite trend to those of Ti and In, namely the diffusion parallel to the [001] axis is faster than that perpendicular to the axis. The predominant process of diffusion perpendicular to the [001] axis has been discussed from a viewpoint of activation energy using the expression of the diffusion coefficients in L10-ordered alloys.