The impurity diffusion of Al was studied in the hexagonal close-packed α-phase. The samples included ultra-pure material having extremely low concentrations of interstitial impurities such as Fe, Co and Ni. In-depth profiling by secondary ion mass spectrometry was used for diffusion measurements both perpendicular to, and parallel to, the c-axis. The results for the ultra-pure α-phase, perpendicular to the c-axis, could be described by:

D (cm2/s) = 6.6 x 101 exp[-78.3(kcal/mol)/RT]

The ratio of the parallel diffusivities to the perpendicular diffusivities was equal to about 0.65.

M.Köppers, C.Herzig, M.Friesel, Y.Mishin: Acta Materialia, 1997, 45[10], 4181-91