The diffusion coefficients were measured at temperatures ranging from 489 to 774K. The 16O was injected via ion implantation. The diffusion penetration profiles were then measured by exploiting the 16O(d,p)17*O nuclear reaction. The temperature dependence of the O diffusivity was described by:

D (m2/s) = 1.3 x 10-6 exp[-121.6(kJ/mol)/RT]

It was found that the addition of Si and Al hardly affected O diffusion, whereas the addition of Fe, Nb or B decreased the diffusivity by 20 to 70%, and the addition of Cr or Mo decreased the activation energy by 10 to 15% (table 261). The most marked alloying effect was observed in the case of the V-3Ti-2Si and V-5Ti alloys. The diffusivity in V-5Ti was about 2 orders of magnitude lower than that in V. It was concluded that this was evidence for a trapping effect due to Ti, and the binding energy was estimated to be about 52kJ/mol.

H.Nakajima, S.Nagata, H.Matsui, S.Yamaguchi: Philosophical Magazine A, 1993, 67[3], 557-71

Table 262

Diffusivity of V in V