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  axis. The diffusion of Ti and In perpendicular to the  axis is faster than that parallel to the  axis. However, the diffusion anisotropies of Fe and Ni show opposite trend to those of Ti and In, namely the diffusion parallel to the  axis is faster than that perpendicular to the axis. The predominant process of diffusion perpendicular to the  axis has been discussed from a viewpoint of activation energy using the expression of the diffusion coefficients in L10-ordered alloys.
Andreas Öchsner and José Grácio
H. Nakajima et al., "Self- and Impurity Diffusion in γ-TiAl Single Crystals", Defect and Diffusion Forum, Vols. 258-260, pp. 259-269, 2006