Diffusion in the bulk metallic glasses, Zr46.7Be27.5Ni10Ti8.3Cu7.5 and Zr41Be22.5Ni10Ti14Cu12.5, was studied by using secondary ion mass spectrometry for concentration depth-profiling. The Al and Hf tracers were used as substitutes for Zr and Ti because of their similar sizes and because Hf belonged to the same period. It was found that the diffusivities of B, Fe and Co obeyed different Arrhenius laws above and below about 585K. The activation energies in the high-temperature regime were much higher than those in the low-temperature range. In the case of the larger, Al and Hf atoms, no deviation was detected from a simple Arrhenius-type behavior. The results for these diffusants could be described by:

Al:     D (m2/s) = 3.19 x 1012 exp[-4.09(eV)/kT]

Hf:     D (m2/s) = 3.76 x 1010 exp[-3.85(eV)/kT]

The overall trend of the results was that of increasing activation energy with increasing atom size.

Impurity Diffusion in ZrTiCuNiBe Bulk Metallic Glasses. T.Zumkley, M.P.Macht, V.Naundorf, J.Rüsing, G.Frohberg: Journal of Metastable and Nanocrystalline Materials, 2000, 8, 135-9