SKM 2023 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 40: Mechanical Properties and Allloy Design
MM 40.5: Vortrag
Donnerstag, 30. März 2023, 16:45–17:00, SCH A 251
Dynamical and structural properties of undercooled Cu-Ti melts — •Lucas Kreuzer1,2, Fan Yang2, Thomas Hansen3, Andreas Meyer2,3, and Winfried Petry1 — 1Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany — 2Institute for Material Physics in Space, German Aerospace Center (DLR), Cologne, Germany — 3Institute Laue-Langevin (ILL), Grenoble, France
Cu-Ti alloys feature a large, undercooled liquid region and a high glass-forming ability (GFA) and thus, provide the possibility to obtain two component bulk metallic glasses (BMGs). This unusual behavior could be due to the special properties of the liquid Cu-Ti system: a positive excess volume and a negative enthalpy of mixing. However, the relevant atomic mechanisms responsible for such good GFA are still to be explored. Here we discuss the temperature-dependent dynamical and structural properties of Cu-Ti melts, within a compositional range of 24 to 69 at% Ti. Accurate data about viscosity, density, and atomic structure, the Cu-Ti samples was obtained by using have been processed without any container using the electrostatic levitation technique. We found a non-monotonous trend of the viscosity, with the highest values at intermediate Ti contents. Surprisingly, this dynamical trend is not reflected by the macroscopic packing fraction, meaning a high viscosity does not necessarily correlate with a dense packing. However, on the atomic scale, x-ray and neutron diffraction reveal a denser, local packing and a pronounced chemical short-range order. These short-range interactions can explain the high viscosity, while the macroscopic packing fraction is rather governed by long-range interactions.