Berlin 2015 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
MM: Fachverband Metall- und Materialphysik
MM 41: Electron Microscopy
MM 41.5: Vortrag
Mittwoch, 18. März 2015, 16:45–17:00, TC 006
Determination of local density in amorphous materials based on HAADF-STEM signals — •Lea Kümper1, Vitalij Schmidt1, Harald Rösner1, Martin Peterlechner1, Tobias Brink2, and Gerhard Wilde1 — 1Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Germany — 2Institut für Materialwissenschaft, Technische Universität Darmstadt, Germany
It was shown that in metallic glasses narrow zones with different densities in comparison to the surrounding matrix are formed during plastic deformation. These deformation zones are called shear bands. Using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) it is possible to quantify the local density changes in amorphous materials and thus in shear bands [1]. The quantification of the local density change ρ was based on the approximation that the density change can be calculated according to: Δρ=ρ1−ρ2/ρ2≅I1 xk1 t2/I2 xk2 t1 −1 , where ρ is the density, xk is the contrast thickness and t is the foil thickness for different zones in a sample. In this contribution the reliability of this approximation is investigated experimentally using amorphous Si-Ge multilayer systems as calibration standards. Additionally, we obtained Cu-Zr glass structures with shear bands by molecular dynamics computer simulations. These were used to obtain the corresponding HAADF-STEM images via image simulation. The obtained results are discussed with respect of the accuracy of the density determination method. [1] H. Rösner et al., Ultramicroscopy, 142 (2014)