Dresden 2017 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 56: Topical session: Dynamics, relaxation and deformation in deeply supercooled metallic liquids and glasses - kinetic transitions
MM 56.4: Vortrag
Donnerstag, 23. März 2017, 11:15–11:30, IFW A
Indications for a kinetic crossover in bulk metallic glasses — •Stefan Küchemann1, Robert Maass1, and Konrad Samwer2 — 1Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA — 21. Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, Germany
In the supercooled liquid, kinetic crossovers strongly alter the dynamics of glass-forming alloys leading, for instance, to the breakdown of the Stokes-Einstein relation and the emergence of a secondary relaxation mode. Measurements of the static structure factor during ultrafast heating experiments of metallic glasses reveal an underlying structural transition which occurs in the close vicinity of the kinetic crossover in the supercooled liquid [1]. In this contribution we provide evidence that a kinetic crossover also occurs in the glass state. By covering an extended range of heating rates from very slow to ultrafast we are able to show that the glass transition temperature as a function of heating rate deviates from the expected Vogel-Fulcher-Tamann behavior [2]. At this crossover the amorphous structure rejuvenates despite the exposure to elevated temperatures which changes the mechanical properties. The results are discussed in the framework of an underlying thermodynamic phase transition.
The authors acknowledge the financial support by the DFG within FOR1394 in P1.
[1] S. Küchemann and K. Samwer, Acta Materialia 104, 119 (2016). [2] S. Küchemann, G. Gibbins, J. Corkerton, E. Brug, J. Ruebsam, and K. Samwer, Philosophical Magazine Letters, 1 (2016).