The behavior of H was determined by using the gaseous permeation method at 473 to 1073K, under partial pressures of between 0.01 and 0.1MPa:

3at%Ni (fcc):     D (cm2/s) = 1.14 x 10-3 exp[-31.4(kJ/mol)/RT]

3at%Ni (bcc):     D (cm2/s) = 1.93 x 10-4 exp[-9.62(kJ/mol)/RT]

5at%Ni (fcc):     D (cm2/s) = 1.16 x 10-3 exp[-47.7(kJ/mol)/RT]

5at%Ni (bcc):     D (cm2/s) = 2.76 x 10-4 exp[-6.95(kJ/mol)/RT]

6at%Ni (fcc):     D (cm2/s) = 6.19 x 10-5 exp[-15.2(kJ/mol)/RT]

6at%Ni (bcc):     D (cm2/s) = 1.20 x 10-4 exp[-5.54(kJ/mol)/RT]

9at%Ni (fcc):     D (cm2/s) = 3.15 x 10-3 exp[-39.8(kJ/mol)/RT]

9at%Ni (bcc):     D (cm2/s) = 4.27 x 10-4 exp[-10.8(kJ/mol)/RT]

12at%Ni (fcc):     D (cm2/s) = 1.08 x 10-4 exp[-12.1(kJ/mol)/RT]

12at%Ni (bcc):     D (cm2/s) = 8.34 x 10-5 exp[-6.62(kJ/mol)/RT]

20at%Ni (fcc):     D (cm2/s) = 1.55 x 10-2 exp[-51.7(kJ/mol)/RT]

20at%Ni (bcc):     D (cm2/s) = 8.78 x 10-5 exp[-6.01(kJ/mol)/RT]

40at%Ni (fcc):     D (cm2/s) = 4.92 x 10-4 exp[-25.5(kJ/mol)/RT]

50at%Ni (fcc):     D (cm2/s) = 3.76 x 10-3 exp[-36.4(kJ/mol)/RT]

The Arrhenius plot of the diffusivity values for Fe-Ni alloys which contained less than 30at%Ni exhibited a sudden change. This was due to the influence of the body-centered cubic to face-centered cubic martensitic transformation. The activation energies for diffusion in the face-centered cubic phase were larger than those in the body-centered phase.

Y.Yamanishi, T.Tanabe, S.Imoto: Transactions of the Japan Institute of Metals, 1983, 24[1], 49-58