The tracer diffusion coefficients of H in the body-centered cubic ß-phase of TiH0.57 and TiH0.70 were measured at temperatures ranging from 620 to 830K. The tracer diffusion coefficients of H in the alloy hydrides, Ti0.96V0.04Hx and Ti0.92V0.8Hx, were measured for x-values of between 0.39 and 0.70, over a similar range of temperatures. The results which were obtained by using the nuclear magnetic resonance alternating pulsed field gradient spin echo technique could be fitted to Arrhenius expressions (table 167). The activation energies ranged from 0.115 to 0.155eV/atom, and the pre-exponential factors were typical of body-centered cubic group-V transition metal hydrides. At temperatures where a mixture of a and ß phases was present, deviations from the Arrhenius relationship were observed. These were attributed to the effects of restricted diffusion. In all of the samples, the spin-lattice relaxation times were found to fit a Korringa relationship. The constant in this relationship exhibited a weak dependence upon the V or H concentrations. The addition of 4at%V to Ti lowered the transformation temperature (to the body-centered cubic phase) by about 40K with respect to the transformation temperature for pure TiHx.

E.H.Sevilla, R.M.Cotts: Physical Review B, 1988, 37[12], 6813-20

Table 167

Diffusion of H in Ti and Ti-V Alloys