The impurity diffusion of Al was studied in the hexagonal close-packed a-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 a-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

The best linear fits to the solute diffusion data ([1204] to [1206], [1226] to [1227], [1234] to [1237]) yield:

Al: Ln[Do] = 0.46E – 31.1 (R2 = 0.998); O: Ln[Do] = 0.28E – 11.8 (R2 = 0.77);

Ti: Ln[Do] = 0.25E – 17.1 (R2 = 0.85)