Kinetik- und Strukturuntersuchung von unterkühlten Zr-basierten metallischen massivglasbildenden Flüssigkeiten
Zusammenfassung der Projektergebnisse
In summary, in the current project we studied a series of metallic glass-forming alloy melts in respects to the characteristics and the mechanism of the strong-fragile transition, varying the number of components of the alloys systematically from 3 to 5. In all these studied melts, we were able to accurately determine the liquid viscosity at temperatures from equilibrium melt down to glass transition. With these results, a mismatch in the temperature dependence between the high and low temperature regimes can be confirmed, which is independent of the number of components for the investigated compositions, indicating the presence of a strong-fragile transition in the undercooled melt. The strong-fragile transition does not only manifest itself in the kinetics of the melt, but is also accompanied by structural and thermodynamic signatures, namely, a sudden change in the temperature dependence of the structure factor maximum position, and an increase in the heat capacity. However, the density of the melts exhibits no significant changes. For the two alloy compositions Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit1) and Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 (Vit106a), where the temperature range where the transition occurs can be directly accessed, we found that the transition kinetics are on the order of tens of seconds, indicating that long range mass transport is necessary. Such slow transition kinetics are incompatible with an underlying mechanism involving local structural changes only. Thus, the mechanism of the strong-fragile transition in metallic melts seems to be quite unique, which is distinct from that in oxides, water or other molecular liquids.
Projektbezogene Publikationen (Auswahl)
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Liquid-Liquid transition in a strong bulk metallic glass-forming liquids, Nat. Comm., 4, 2083 (2013)
S. Wei, F. Yang, J. Bednarcik, I. Kaban, O. Schuleshova, A. Meyer, and R. Busch
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Kinetic, thermodynamic, and structural transitions in order-disorder alloys and bulk metallic glass-forming alloys, Dissertation, Universität des Saarlandes, 2014
Shuai Wei
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High temperature rheology of Zr-based bulk metallic glass forming liquids, Dissertation, Universität des Saarlandes, 2015
William Hembree
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Linking structure to fragility in bulk metallic glass-forming liquids, Appl. Phys. Lett., 106, 181901 (2015)
S. Wei, M. Stolpe, O. Gross, Z. Evenson, I. Gallino, W. Hembree, J. Bednarcik, J. J. Kruzic, R. Busch
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Structural changes during a liquid-liquid transition in the deeply undercooled Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glass forming melt, Phys. Rev. B, 93, 014201 (2016)
M. Stolpe, I. Jonas, S. Wei, Z. Evenson, W. Hembree, F. Yang, A. Meyer, R. Busch
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Thermophysical and structural properties of the equilibrium and undercooled melt of bulk metallic glasses investigated by electrostatic levitation, Dissertation, Universität des Saarlandes, 2016
I. Jonas
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High-temperature rotating cylinder rheometer for studying metallic glass forming liquids, Rev. Sci. Instrum., 89, 113904 (2018)
W. Hembree, B. Bochtler, R. Busch
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Industrial grade versus scientific pure: Influence on melt properties, Appl. Phys. Lett., 112, 171902 (2018)
I. Jonas, W. Hembree, F. Yang, R. Busch, A. Meyer
