Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 43: Liquid and Amorphous Metals II

MM 43.3: Vortrag

Donnerstag, 26. März 2009, 16:30–16:45, IFW A

Temperature and kinetics of shear band propagation in amorphous metals — •Florian H. Dalla Torre, David Klaumünzer, Alban Dubach, and Jörg F. Löffler — Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich, Switzerland

Deformation in bulk metallic glasses (BMGs) far below their glass transition temperature is known to be spatially inhomogeneous and restricted to narrow nanometer-sized shear bands. In this study the shear band characteristics of Zr-based BMGs has been investigated as function of strain rate and temperature. To capture discrete shear events precisely a dedicated acoustic emission spectrometer has been used in-situ during deformation testing, which allows for extremely high data acquisition rates of the order of MHz. Preliminary results of evaluating the viscosity within shear bands during deformation suggest that the local temperatures are of the same order of magnitude as those measured during homogeneous deformation close to the glass transition temperature. Acoustic emission results indicate that irreversible deformation starts well before reaching the elastic limit and that the Kaiser effect known to crystalline metals is present also in amorphous metals. It is shown that serrated flow and the associated stress drops are a function of temperature and strain rate. The time periods for a shear band to be activated increases with decreasing temperature from milliseconds at ambient temperatures to seconds at temperatures of 200 K.