Measurements were made of H migration, in cryoformed samples, by using a gas-phase permeation technique. The specimens contained about 90% of α' martensite. It was found that the H diffusivity, described by:

D (cm2/s) = 3.7 x 10-2 exp[-41.4(kJ/mol)/RT]

was between the values for α- and γ-type steels. The separation of the permeation values, as described by:

P (cm3/cm s Pa½) = 1.57 x 10-5 exp[-43.5(kJ/mol)/RT]

was less clear. The difference between the activation energies for diffusion and permeation was considered to be anomalously low.

T.P.Perng, C.J.Altstetter: Scripta Metallurgica, 1984, 18[1], 67-70