Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 38: Liquid and Amorphous Metals

MM 38.1: Vortrag

Mittwoch, 28. März 2012, 15:00–15:15, H 1029

Probing Shear-Band Initiation in Metallic Glasses — •David Klaumünzer, Robert Maass, Peter Thurnheer, and Jörg F. Löffler — Laboratory of Metal Physics and Technology, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland

At low homologous temperatures, metallic glasses are known to deform inhomogeneously by the formation of nanometer-sized shear bands. Typically, the operation of these bands is intermittent as reflected in serrated flow curves. This can be best understood in the context of stick-slip in which extended periods of arrest are followed by rapid slip events. The strong localisation of flow in space coupled with the fast operation of shear bands poses severe experimental challenges. We have approached this problem by using in-situ acoustic emission monitoring during compression testing of a Zr-based metallic glass. With this method, the mechanism of shear-band initiation prior to each slip event can be resolved. By drawing an analogy to the intermittent flow behaviour of granular media, we attribute the acoustic emission signal to a local volume expansion within a shear band. A quantitative analysis reveals volume changes for shear band initiation of a few percent only, in agreement with the excess free volume typical of the supercooled liquid regime.

[1] D. Klaumünzer et al., Physical Review Letters 107, 185502 (2011).