Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 44: Mechanical properties III

MM 44.2: Vortrag

Freitag, 30. März 2007, 12:45–13:00, H6

Deformation kinetics in Zr-based bulk metallic glasses — •Alban Dubach, Florian Dalla Torre, and Jörg Löffler — Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich, Switzerland

While deformation and flow in crystalline materials can be generally described in terms of the underlying dislocation dynamics, a corresponding formalism for disordered systems is intrinsically less defined. The latter class of materials also includes amorphous metals, which, compared to their crystalline counterparts, exhibit higher yield strength and elastic strain limit, but unfortunately suffer from low ductility at room temperature due to the formation of highly-localized shear bands.

Detailed micromechanical analysis of Zr-based bulk metallic glasses at various temperatures and strain rates facilitate accurate measurements of the inhomogeneous flow kinetics. Our results suggest a micromechanical deformation mechanism based on two processes: shear displacement through the formation and propagation of shear transformation zones, and diffusive structural relaxation processes in the distorted structure. The latter cease below a critical temperature (or above a critical strain rate), resulting in the disappearance of flow instabilities (i.e. serrations) correlated with a change in the strain rate sensitivity. Based on these findings, a constitutive deformation model is presented and similarities with the dynamic strain aging effect known for crystalline metals are elucidated.