Impurity diffusion in γ-TiAl single crystals

The diffusion coefficient of In in γ-TiAl single crystals has been measured using the ion implantation technique and secondary ion mass spectrometry in order to clarify the diffusion anisotropy: the diffusion perpendicular and parallel to the [0 0 1] axis. The diffusion of In perpendicular to the [0 0 1] axis is faster than that parallel to the [0 0 1] axis. Such diffusion anisotropy is similar to that of Ti previously investigated by our group. The diffusion coefficients of Fe and Ni have also been measured. The diffusion anisotropies of Fe and Ni show an opposite trend to those of In and Ti, namely the diffusion parallel to the [0 0 1] axis is faster than that perpendicular to this axis. The predominant process of diffusion perpendicular to the [0 0 1] axis is discussed from the viewpoint of activation energy using the expressions of the diffusion coefficients in L10-ordered alloys.