Nanocrystalline samples with average grain sizes of 15 to 200nm were produced by the recrystallization of melt-spun amorphous ribbons. After H-charging, the diffusion of H was monitored by using magnetic after-effect and thermal desorption techniques. It was found that the nanocrystalline Fe-Zr and Fe-Co-Zr alloys exhibited a marked concentration dependence of the short-range and long-range H diffusion. This was characteristic of the existence of a statistical distribution of interstitial sites and saddle-point enthalpies. The origin of these statistical diffusion potentials was attributed to the interfacial regions. The grains of these alloys had a high H solubility. The nanocrystalline Co-Zr alloy exhibited no concentration dependence of the H diffusivity. The desorption kinetics, over a wide range of grain sizes, indicated that the H was dissolved mainly in the grains and diffused very rapidly in the interfacial regions. The de-gassing rate depended upon the grain size, and obeyed Einstein’s diffusion law.

M.Hirscher, J.Mossinger, H.Kronmuller: Nanostructured Materials, 1995, 6[5-8], 635-8