Microscopic structure and dynamics of bulk metallic glass-forming liquids with minor additions

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Within the current project the microscopic dynamics, viscosity, and the crystallization behavior of the Zr-Cu melts have been studied employing quasielastic neutron scattering, oscillating drop technique, and in-situ synchrotron diffraction, respectively, all combined with the containerless processing technique of electrostatic levitation. We were able to show that alloying a small amount of Al, 4 at %, notably alters the dynamics, as well as the solidification behavior from deeply undercooled melt at Zr50Cu50 liquid. In contrast, the impact of a small Ti addition on the melt dynamics is considerably smaller. First molecular dynamics simulations indicate, that the strong compositional dependence of the melt dynamics upon Al addition may have its origin in the medium range of the liquid. Hence, contributions from chemical short-range order are expected to play an important role in the melt, too. To test this hypothesis i) we intend to alloy a third, non-metallic element like Si (instead of Al) where the impact of the electronic interactions would be even more dominant in metal/non-metal atomic pairs and to apply ii) fluctuation electron microscopy (FEM) to address the important question as to the structural role of the minor addition on glass-forming ability. Together with theory and simulation, this project seeks to better understand the nature of bulk metallic glass formation by identifying the key microscopic role played by the minor addition in enhancing the glass-forming ability of binary alloys. In the framework of the continuation Mr. Szabo will finish his PhD thesis.