Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 44: Quasicrystals II

MM 44.1: Vortrag

Donnerstag, 26. März 2009, 14:00–14:15, IFW B

In situ observation of the formation of the metastable decagonal quasicrystalline D-phase in Al-Ni melts — •Dirk Holland-Moritz¹, Olga Shuleshova², Wolfgang Löser², Guillaume Reinhart³, and Thomas Buslaps⁴ — ¹Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany — ²Leibnitz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden, 01171 Dresden, Germany — ³ESA External Research Fellow, ESRF / ILL, 38042 Grenoble, France — ⁴ESRF, 38043 Grenoble, France

The phase selection during solidification of undercooled Al-Ni melts is investigated by time-resolved in situ measurements using a combination of electromagnetic levitation technique and energy dispersive diffraction of synchrotron radiation. For the investigated alloys in the composition range of 18 - 31.5 at.% Ni undercooling below the liquidus temperature does not influence the selection of the primary solid phase even at highest levels of undercooling. If the semi-solid samples are cooled to lower temperatures we were able to undercool the peritectic reaction during which under equilibrium conditions Al₃Ni is formed. If a sufficient undercooling below the peritectic temperature is obtained a metastable phase is formed, that is identified as the decagonal quasicrystalline D-phase. It subsequently transforms and can only be conserved up to room temperatures if sufficiently high cooling rates are applied. Financial support from the European Commission EU within the IMPRESS Integrated Project under contract FP6-500635-2 and the provision of beamtime by ESRF are gratefully acknowledged.