Short-range order in undercooled metallic melts and its influence on nucleation

Dirk Holland-Moritz

DLR, Institut für Raumsimulation, Kön, Germany

This work presents investigations on the short-range order of stable and deeply undercooled liquids of the pure elements (Ni, Co, Zr, Ti and Fe) and of alloys forming quasicrystalline or polytetrahedral phases (Al60Cu34Fe6, Al65Cu25Co10, Al13(Fe,Co)4 and Ti72.3Fe27.7). The liquids were containerlessly processed and undercooled by application of the electromagnetic levitation technique, which was combined with elastic neutron scattering at the Institute-Laue-Langevin (ILL) in Grenoble and with energy dispersive diffraction of synchrotron radiation at the European Synchrotron Radiation Facility (ESRF) in Grenoble in order to determine the structure factors of the liquids as a function of the temperature. For all of the investigated metallic liquids the experiments provide evidence of an icosahedral short-range order prevailing in the melt. The impact of this icosahedral short-range order on the energy of the interface between the melt and a nucleus of a solid phase is discussed, which decisively influences the nucleation behaviour.

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