Internal friction measurements were performed by using a torsion pendulum which was modified for use in a vacuum. Elastic after-effect experiments were performed by using the same equipment. The wires (0.76mm diameter) were surface-cleaned before testing. On this basis, H diffusivities were deduced from the internal friction results. Diffusion coefficients were also calculated by using a tetrahedral model. The diffusivity (octahedral model) was described by:

D (m2/s) = 5.21 x 10-7 exp[-158.48(kJ/mol)/RT]

H.Kokawa, T.Watanabe, A.Uehara, S.Karashima: Scripta Metallurgica, 1978, 12[4], 357-9