The effect of an oxide layer upon the diffusion of T in single crystals which had been pre-treated in air (0.5h, 20 to 350C) was studied by using radio-tracer methods at 150 to 550C. At a given temperature, the diffusivity in the [110] direction was 10 to 15% lower than in the [100] direction. This was attributed to a difference in the oxidation tendency of the various faces. The temperature dependence of T volume diffusion in the single crystals was given by:

D (cm2/s) = 0.001 exp[-15400/RT]

and did not depend upon the metal structure. The presence of O in the surface layer had a considerable effect upon T diffusion.

T.M.Maksumov, E.E.Petushkov: Doklady Akademii Nauk Uzb. SSR, 1974, 31[9], 32-4 and 31[10], 24-6