Analytical transmission electron microscopy applied to the characterization of deformation in metallic glasses

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Abstract

Plastic deformation of metallic glasses performed well below the glass transition temperature leads to shear localization and finally to the formation of shear bands. To elucidate the underlying mechanisms of shear band formation, microstructural investigations were carried out on sheared zones using analytical transmission electron microscopy. Different electron-scattering signals were collected from the shear bands and their surrounding matrix to obtain information regarding density and medium-range order (MRO). Qualitatively similar features were observed for three different types of metallic glasses representing fragile to ductile states. A model for the post-deformation state derived from continuum mechanics is presented describing this generic deformation behavior in terms of Eshelby-like quadrupolar stress fields. Moreover, the investigations reveal that materials softening and shear band formation/propagation is related to changes in the MRO. The results indicate the significance of MRO in deformation of metallic glasses and suggests that the ductility of monolithic BMGs can be improved by tailoring topological order based on MRO types, sizes and volume fractions.

Speakers from the University of Münster

Rösner, Harald

Professorship of Materials Physics (Prof. Wilde)