Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 13: Liquid and Amorphous Metals III: Mechanical properties

MM 13.1: Vortrag

Montag, 7. März 2016, 15:45–16:00, H52

Thermal relaxation of metallic glasses: Influence on mechanical properties and structure studied by molecular dynamics simulations — •Tobias Brink and Karsten Albe — Fachgebiet Materialmodellierung, Institut für Materialwissenschaft, Technische Universität Darmstadt, Germany

Metallic glasses show a transition from homogeneous deformation to shear banding depending on temperature and strain rate, with shear banding being the typical mechanism at ambient conditions. The critical values for the transition are determined by the glass composition but should also depend on the structure of the glass. We use molecular dynamics computer simulations to investigate the deformation mechanism in as-quenched and annealed Cu₆₄Zr₃₆ metallic glasses. Due to the very high strain rates in the simulation, the as-quenched glass only exhibits shear banding at low temperatures. In contrast, shear banding occurs at the same strain rates well above room temperature in samples that were annealed for several hundred nanoseconds near T_g. Additionally, properties like structure, short-range order, potential energy, free volume, and vibrational properties (boson peak) change with annealing time, indicating a more relaxed metallic glass, i.e., a decreased fictive temperature. We discuss the shear banding at elevated temperatures in terms of these structure-related changes. Furthermore, we investigate the influence of thermal relaxation on pre-existing shear bands and compare their structural relaxation to that of the matrix.