The behavior of H was determined by using the gaseous permeation method, at temperatures of between 473 and 1073K, under partial pressures of between 0.01 and 0.1MPa. An Arrhenius plot of the diffusivity values for pure Fe was linear down to temperatures as low as 473K. The permeability and diffusivity (tables 41 and 42) in Fe-alloys which contained less than 30at%Ni exhibited sudden changes which were due to the body-centered cubic to face-centered cubic martensitic transformation. The activation energies for permeation and diffusion in the face-centered cubic phase were larger than those in the body-centered phase. The variation of the permeability and diffusivity as a function of alloy composition was complex, but the values tended to lie between those for the pure metals. The logarithm of the pre-exponential term was linearly related to the activation energy.
Hydrogen Permeation and Diffusion through Pure Fe, Pure Ni and Fe-Ni Alloy. V.Yamanishi, T.Tanabe, S.Imoto: Transactions of the Japan Institute of Metals, 1983, 24[1], 49-58
Table 42
Parameters for H Diffusion in Fe-Ni
Ni (at%) | Phase | Do (m2/s) | E (kJ/mol) |
0 | bcc | 6.20 x 10-8 | 10.5 |
3 | fcc | 1.14 x 10-7 | 31.4 |
3 | bcc | 1.93 x 10-8 | 9.62 |
5 | fcc | 1.16 x 10-7 | 47.7 |
5 | bcc | 2.76 x 10-8 | 6.95 |
6 | fcc | 6.19 x 10-9 | 15.2 |
6 | bcc | 1.20 x 10-8 | 5.54 |
9 | fcc | 3.15 x 10-7 | 39.8 |
9 | bcc | 4.27 x 10-8 | 10.8 |
12 | fcc | 1.08 x 10-8 | 12.1 |
12 | bcc | 8.34 x 10-9 | 6.62 |
20 | fcc | 1.55 x 10-6 | 51.7 |
20 | bcc | 8.78 x 10-9 | 6.01 |
40 | fcc | 4.92 x 10-8 | 25.5 |
50 | fcc | 3.76 x 10-7 | 36.4 |
100 | fcc | 7.43 x 10-7 | 44.1 |
Table 43
Electrotransport of H and D in -Fe
Isotope | Temperature (C) | Current (A) | Z*(e) |
H | 441 | 66.5 | 0.22 |
H | 450 | 22.7 | 0.23 |
H | 457 | 68.4 | 0.25 |
H | 500 | 70 | 0.26 |
H | 550 | 73 | 0.23 |
D | 463 | 63 | 0.38 |
D | 536 | 68 | 0.39 |