Dresden 2017 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 4: Topical session: Dynamics, relaxation and deformation in deeply supercooled metallic liquids and glasses I - Structural Transitions

MM 4.1: Topical Talk

Montag, 20. März 2017, 10:15–10:45, IFW A

Structural transition upon vitrification in viscous metallic liquids — •Andreas Meyer — Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, Köln

We investigate vitrification of bulk-glass forming Zr-Ni-Cu-Ti-Be and Zr-Cu-Ni-Al-Nb liquids from the equilibrium melt to the glass transition in-situ with container-less processing. Electrostatic levitation gives access to the measurement of temperature, density and in combination with X-ray diffraction to the total structure factor. Free radiation cooling of the sample allows the measurement of the specific heat over constant emissivity of the sample, which exhibits a pronounced peak in the deeply undecooled melt. This comes along with a change in the temperature dependence of the position of the first sharp diffraction peak, whereas the thermal expansion of the sample does not exhibit a detectable change over the entire temperature range. In addition, indirect information on the specific heat of the sample is obtained by precise measurement of the required heating laser power. All measurements reveal a consistent onset of changes in the total structure factor and the specific heat with no detectable cooling rate dependence. Results are discussed in the context of liquid-liquid phase transitions and the mode coupling theory of the liquid to glass transition.