An appreciable sub-scale hardening was observed in these alloys after exposure to O2, N2 or N2-20O2 at 1300K. The diffusivities of N and O (table 30) were then deduced from micro-hardness profiles. It was found that the diffusivities were comparable to those that had been reported for -Ti. The diffusivity of O in Ti-24Al-15Nb was close to the values that had been reported for O diffusion in Ti-25Al-11Nb.

T.K.Roy, R.Balasubramaniam, A.Ghosh: Scripta Materialia, 1996, 34[9], 1425-30

Table 30

Diffusivities of O and N in Ti-25Al and Ti-24Al-15Nb at 1300K