Berlin 2005 – scientific programme

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M: Metallphysik

M 23: Phasenumwandlung III

M 23.2: Talk

Saturday, March 5, 2005, 15:00–15:15, TU H1058

In-situ Determination of Phase Selection Sequences and Short-Range Order in Undercooled Ti-Fe-Si-O Melts — •Oliver Heinen, Dirk Holland-Moritz, Thomas Volkmann, Jörn Strohmenger, and Dieter M. Herlach — DLR, Inst. für Raumsimulation, D-51170 Köln

The alloy system Ti-Fe-Si-O shows a great variety of complex stable and metastable phases. Depending on composition and undercooling different solidification pathways are found. The large number of alloy phases in Ti-Fe-Si-O leads to a strong competition of phase selection during rapid solidification of undercooled melts. In order to determine the phase formation sequence as function of composition and to examine possible dependencies on the short-range order (SRO) of the undercooled liquid, in situ investigations of SRO and solidification pathways were performed. The containerless processing technique of electromagnetic levitation was combined with energy dispersive diffraction of synchrotron radiation at the European Synchrotron Radiation Facility. This enables us to directly determine the crystal structure of the solid phases formed during rapid solidification and to study the SRO of the liquid in the same experiment. Depending on the undercooling different solidification sequences were found. In addition the SRO was also investigated using neutron diffraction at the Institut Laue-Langevin. The complementary results on the SRO obtained by neutron and x-ray diffraction are discussed in terms of the effects of topological and chemical SRO.

This work was financially supported by DFG under contract No. Ho1942/4 and by ESRF and ILL.