The tracer volume diffusion of 63Ni in Ni-50.07at%Ti binary and Ni-48.83Ti-9.29at%Cu ternary alloys was measured between 783 and 1288K (table 214). It was found that the temperature dependence of the diffusion coefficient could be closely described by:

D (m2/s) = 1.8 x 10-8 exp[155(kJ/mol)/RT]

This illustrated that any diffusional anomaly, which was typical of some body-centered cubic metallic alloys and could be related to phonon softening, was negligible. However, the small activation energy (about half of that expected from simulations of the accepted mechanism, with thermally activated vacancies) showed that the diffusion mechanism was probably mediated by structural vacancies.

J.Bernardini, C.Lexcellent, L.Daróczi, D.L.Beke: Philosophical Magazine, 2003, 83[3], 329-38

Table 210

Diffusion of Co in Ni-Sn Alloys