The nano-range and long-range diffusion of H in amorphous, nanocrystalline, microcrystalline, and heterogeneous transition-metal alloys were studied by using magnetic after-effect and thermal desorption spectrometric methods, respectively. Microstructural and thermodynamic parameters, such as the grain size or the solubility in the interfacial and matrix phases, exerted a marked effect upon H diffusion. In amorphous and nanocrystalline Fe90Zr10 and Fe60Co30Zr10, the mean activation enthalpy for H diffusion decreased with increasing H concentration. This behavior (which was common in amorphous alloys) was attributed to a topologically disordered interfacial phase which had a high H solubility. On the other hand, heterogeneous Co90Zr10 alloys exhibited no dependence of activation enthalpy upon the H concentration. In addition, the desorption kinetics which were observed over a wide range of grain sizes indicated that H dissolved mainly in the crystalline grains and diffused very rapidly in the interfacial phase. A theoretical analysis treated H diffusion in heterogeneous systems by using Monte Carlo simulations. The model system consisted of cubic grains that were separated by an interfacial layer in 3 dimensions. The effective diffusion coefficient was calculated, as a function of the volume fraction of the grains, for various potential barriers between the grains and interfacial phase.

M.Hirscher, J.Mössinger, H.Kronmüller: Journal of Alloys and Compounds, 1995, 231, 267-73