The subject of this investigation is the diffusion in bulk metallic glasses, i.e. amorphous alloys produced with a size in the mm to cm range in all three dimensions. The diffusion is of particular interest from a fundamental point of view – because the adoption of the mechanisms known in crystalline materials is limited – and also with regard to potential applications, because diffusion is a crucial factor for crystallization. To elucidate the mechanisms of diffusion in bulk metallic glasses, in particular compared with the familiar conventional amorphous alloys, the impurity diffusion was investigated varying a multitude of experimental parameters, viz the dependence on the composition of the alloy, the atomic size of the tracer, the mass and pressure dependence of diffusion as well as radiation enhanced diffusion. The samples were prepared as thin films by thermal evaporation, the diffusion coefficients determined with secondary ion mass spectrometry. The combination of the investigated facets yields a consistent picture, featuring a slowdown of diffusion in bulk metallic glasses with a diminished size dependence. Combined with the small isotope effect parameter and the low pressure dependence, this indicates a collective diffusion mechanism, in accordance with molecular dynamic simulations. | English |