Regensburg 2016 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 40: Topical session: In-situ Microscopy with Electrons, X-Rays and Scanning Probes in Materials Science IV - Atomic structure and defects III
MM 40.5: Talk
Wednesday, March 9, 2016, 17:30–17:45, H38
Medium range order in Pd-based glasses — •Vitalij Schmidt1, Harald Rösner1, Martin Peterlechner1, Gerhard Wilde1, and Paul Vayles2 — 1Insitut für Materialphysik, Universität Münster — 2Materials Science and Engineering, University of Wisconsin-Madison
Metallic glasses exhibit superior mechanical properties like high yield strength or wear and corrosion resistance. However after a large elastic regime they are prone to catastrophic failure especially under tensile load. This motivates an interest in understanding the deformation behavior of metallic glasses. Deformation tests on metallic glasses performed well below the glass transition temperature have shown that the plastic flow is restricted to narrow regions called shear bands. They are associated with a structural changes (free volume) compared to the surrounding matrix due to shear localization. Thus modifications of the local short or medium range order (SRO, MRO) are expected in shear bands.
In order to study directly the structural changes fluctuation electron microscopy (FEM) has been used to characterize Pd-based metallic glass samples by analyzing sets of nanobeam diffraction patterns (NBDPs). The variance of the individual patterns were extracted from azimuthal profiles and normed be the mean intensity squared. This way a directly comparable normalized variance is obtained. Samples of different states (as-cast, deformed, annealed) and chemical compositions (micro-alloying) are compared.