Berlin 2005 – scientific programme

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M: Metallphysik

M 6: Symposium Complex Metallic Alloys I

M 6.2: Talk

Friday, March 4, 2005, 11:15–11:30, TU H1058

Structure-Property Relationships of Complex Intermetallic Phases — •Walter Steurer — Laboratory of Crystallography, Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland

It is amazing how sensitive some physical properties are to slight variations in the chemical composition of a complex intermetallic phase and its thermal history. Experiments on the most complex intermetallic phases, the quasicrystals, have shown that even annealing times of several thousand hours at two third of the melting temperature may be not sufficient to reach the equilibrium state. Non-equilibrium defects such as dislocations and nanodomain structures as well as chemical disorder may locally break the symmetry. In particular, cluster-based structures with a high-degree of pseudosymmetry tend to form orientationally twinned domain structures with rather low interfacial energy.

Materials creation and design crucially depends on materials characterization. Measurements of physical properties are only meaningful if they are reproducible. The results can only be reasonably interpreted and contribute to the understanding of a material if its chemical composition, crystal and defect structure are accurately known. On a few examples, the importance of materials analysis as function of composition, temperature and pressure is demonstrated.