The migration of H in high-purity material was studied by using the Gorsky-effect anelastic technique. The observed H diffusivities depended upon the concentrations of trapping sites such as dislocations and O atoms. At low interstitial solute levels and low dislocation densities (104/cm2), the activation energy was 0.080eV. As the number of O trapping sites increased, the activation energy increased to a value of 0.096eV at 0.23at%O (table 95). The introduction of dislocation trapping sites by cold-rolling (10% reduction of area) increased the activation energy to 0.093eV. High activation energies were also observed in specimens which contained high H concentrations after extensive hydride precipitation had occurred. This was consistent with the large amount of plastic deformation that occurred when such hydrides were precipitating.

G.Matusiewicz, R.Booker, J.Keiser, H.K.Birnbaum: Scripta Metallurgica, 1974, 8[12], 1419-25

Table 95

Parameters for H Diffusion in Nb at Temperatures above 165K