Structural arrest in multicomponent glass-forming Zr-melts
Zusammenfassung der Projektergebnisse
In conclusion, we studied a series of Zr-based glass-forming melts from binary Zr-(Ni,Co,Cu), ternary Zr-(Ni,Co)-Al to the multicomponent Vit1/Vit4 alloys. With QNS the self-diffusion coefficients of Ni/Co/Cu were measured, which were used as reference data for tracer diffusion experiments. We showed that at relatively high temperature, the dynamic decoupling is small, i.e.: within a factor of 2 for all the studied melts. Together with the measured melt viscosity, we also show for Vit4 that the incoherent and incoherent structural relaxation, and hence the self-diffusion and liquid viscosity exhibit very similar temperature dependence. This indicates the Stoke-Einstein relation does not predict the correct temperature dependence of diffusivity from the melt viscosity, although the deviation of absolute value can be small. We also showed that chemical interaction is an important aspect for the composition dependence of the liquid dynamics in these alloys. The Cu dynamics are faster in the Zr-Cu melt compared to that of the Ni/Co in the corresponding Zr-Ni/Co melts, although the atomic sizes of Cu, Ni, and Co are very similar. Alloying Al slows down the melt dynamics of Zr-Ni/Co, which likely have its origin in the strong chemical/electronic interaction between Al and Ni/Co. For interdiffusion our study on the binary Zr-Ni shows that although there is a fairly large thermodynamic driving force in these systems, the Darken relation overestimated the interdiffusion coefficient. This shows that the interdiffusion is dominated by the slow kinetics coefficient, likely due to the high packing fraction of the melt, and the contribution of the cross correlation cannot be neglected. A particularly striking result from our measurements of the decoupling of component tracer diffusivities is that we provided strong evidence for solidlike, i.e. energy-landscape controlled diffusion in bulk metallic glassforming Zr-based equilibrium melts far above the liquidus temperature and many hundred 300 K above the mode coupling temperature Tc. This lends support to the model of local configurational excitations in the atomic connectivity network recently proposed by Egami and co-workers. In these terms, Zr atoms in the melt form significantly stronger temporary nearest neighbor bonds that have to be broken by thermal activation compared to the other atoms. The Egami model is also nicely confirmed by comparing the present data with those obtained in the Pd-based glass forming melt mentioned above. The very reactive Zr has partially occupied d orbitals and can form directed bonds, whereas the noble metal Pd is expected to form much weaker nondirected bonds.
Projektbezogene Publikationen (Auswahl)
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Atomic dynamics in binary Zr-Cu liquids. Europhys. Lett., 107, 46001 (2014)
F. Yang, D. Holland-Moritz, J. Gegner, P. Heintzmann, F. Kargl, C. C. Yuan, G. G. Simeoni, and A. Meyer
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Coupled relaxation processes in a glass forming ZrTiNiCuBe liquid, Europhys. Lett., 107, 26001 (2014)
F. Yang, T. Unruh, and A. Meyer
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Decoupling of component diffusion in a glass forming Zr46.75Ti8.825Cu7.5Ni10Be27.5 melt far above the liquidus temperature, Phys. Rev. Lett. 113, (2014) 165901
S. W. Basuki, A. Bartsch, F. Yang, K. Rätzke, A. Meyer, and F. Faupel
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Atomic dynamics in Zr-(Co,Ni)-al metallic glass-forming liquids. Phys. Rev. B, 91, 214203 (2015)
C. C. Yuan, F. Yang, F. Kargl, D. Holland-Moritz, G. G. Simeoni, A. Meyer
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Diffusion in Zr-based glass forming melts, University of Kiel, PhD Thesis., 2015
Sri Wahyuni Basuki
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Untersuchungen der Zusammenhänge von atomarer Struktur, Selbsdiffusion, Interdiffusion und Viskosität in flussigen Zr-Ni Legierungen. Dissertation, Ruhr-Universität Bochum 2015
Pascal Heintzmann
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Viscosity measurements of metallic melts using the oscillating drop technique. Appl. Phys. Lett. 108, 241908 (2016)
P. Heintzmann, F. Yang, S. Schneider, G. Lohöfer, and A. Meyer
