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M: Metallphysik

M 3: Flüssige und amorphe Metalle II

M 3.4: Vortrag

Freitag, 4. März 2005, 12:15–12:30, TU H111

Diffraction Studies On the Short-Range Order in Metallic Melts — •Dirk Holland-Moritz¹, Thomas Schenk¹, Oliver Heinen¹, Virginie Simonet², Robert Bellissent³, and Dieter M. Herlach¹ — ¹DLR, Institut für Raumsimulation, D-51147 Köln — ²Laboratoire Louis Néel, CNRS, BP166, F-38042 Grenoble Cedex 9 — ³Centre d’Études Nucléaires de Grenoble, DRFMC/SPSMS/MDN, F-38054 Grenoble Cedex

Following the pioneering work of Frank, an icosahedral short-range order should be energetically favoured in undercooled metallic melts. This hypothesis was recently experimentally confirmed by neutron- and X-ray diffraction investigations on stable and undercooled liquids of the pure metals Ni, Co, Zr and Fe and of various alloys forming quasicrystals and polytetrahedral phases. In this work we present experiments on the short-range order of undercooled Co₇₅Pd₂₅ melts. These melts are of special interest because they show the onset of magnetic ordering if they are undercooled close to the magnetic Curie temperature. Moreover, investigations on the short-range order of stable and undercooled melts of Ti are presented. The liquids were containerlessly processed und undercooled by use of the electromagnetic levitation technique which was combined with the technique of energy dispersive diffraction of synchrotron radiation and elastic neutron scattering in order to determine the structure factors. For both sample materials, similar as for most other metallic melts, the measured structure factors are well described if an icosahedral short-range order is assumed to prevail in the melt. This work was supported by DFG under contract Nos. Ho1942/1, Ho1942/2 and Ho1942/4.