The recovery of excess H which was dissolved in Ni-based alloys was studied by using H quenching and electrical resistance techniques during isochronal and isothermal annealing. A recovery stage due to H exhibited the same characteristics as those found for the resistance decay of pure Ni, in that there was a size-dependence of the recovery-rate and shape of the isothermal recovery curves. The H diffusion coefficients (table 122) were deduced for temperatures ranging from 240 to 360K. The high-temperature values were almost the same as those for pure Ni. However, at low temperatures (especially for the Ni-Cu and Ni-Fe alloys), the coefficients were clearly larger than those for pure Ni. It was suggested that the H diffusivity was depressed by trapping at the alloy atoms. This anomalous behavior suggested that grain boundary diffusion became more important in the low-temperature range.

K.Yamakawa, B.Hohler, H.Kronmuller: Journal of Physics - Condensed Matter, 1989, 1[11], 2031-40. See also: Physica Status Solidi A, 1989, 111[1], 89-97

Table 122

Diffusion of H in Ni Alloys at 240 to 360K