Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 36: Topical Session: TEM-Symposium - Structure-Property / In-Situ II
MM 36.1: Vortrag
Mittwoch, 13. März 2013, 11:45–12:00, H25
A novel technique for measuring density changes in shear bands of metallic glasses — •Harald Rösner1, Christian Kübel2,3, Martin Peterlechner1, Joachim Bokeloh1, and Gerhard Wilde1 — 1Institut für Materialphysik, WWU Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany — 2Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology (INT), — 3Karlsruhe Nano Mircro Facility, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany
The deformation process in glasses is different from that in crystalline materials because there is no crystal lattice and consequently no defects such as dislocations, twins or grain boundaries are available as deformation carriers for an easy flow mechanism. Deformation tests on glasses have shown that when the applied load exceeds the elastic range the plastic flow is confined to narrow regions called shear bands. In TEM, shear bands are distinguished from the surrounding amorphous matrix as regions of lower contrast, which is thought to be associated with an increase in free volume and thus a lower density. We describe here a new approach to measure density changes between the amorphous matrix and the shear bands of metallic glasses using the information from electron-energy loss spectra (EELS) and the high-angle annular dark-field scanning transmission electron (HAADF-STEM) signal. We found for melt-spun Al88Y7Fe5 ribbons, surprisingly, an enormous decrease in density in the sheared zones of 6.7%, which we associate with the free volume in the shear bands.