Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 3: Symposium Modern Metallic Materials Design I

MM 3.8: Vortrag

Montag, 27. März 2006, 12:30–12:45, IFW B

Icoshedral connections in complex metallic alloy phases — •Ke Hsin Kuo¹, Z.B. He¹, Ze Zhang², Michael Feuerbacher³, and K. Urban³ — ¹Beijing Laboratory of Electron Microscopy, Institute of Physics, 100080 Beijing, China — ²Beijing University of Technology, 100022 Beijing, China — ³Institut für Festkörperforschung, Forschungszentrum Jlich GmbH, 52425 Jülich, Germany

The crystal structures of a number of complex metallic alloy (CMA) phases in Al-Cr-Si alloys have been determined by X-ray and electron crystallography. The basic structural unit in these structures is the icosahedron with the smaller and minor Cr atom at its center and the somewhat larger Al atom at its vertices. Icosahedra can be connected by mutual penetration along their fivefold axis to form icosahedral chains displaying a pseudo fivefold symmetry. Icosahedra can also be connected by face- and edge-sharing, thus forming chains displaying three- and two-fold symmetry. Consequently, such CMA can form icosahedral/decagonal quasicrystals after very rapid solidification or the crystalline approximants with either cubic (point group m3), hexagonal (6/mmm), orthorhombic (mmm) or monoclinic (2/m) symmetry of these quasicrystals after slow solidification. These structural characteristics will be analyzed with the new structures under investigation.