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Berlin 2005 – scientific programme

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M: Metallphysik

M 11: Symposium Complex Metallic Alloys III

M 11.3: Talk

Friday, March 4, 2005, 18:00–18:15, TU H1058

Plastic behaviour of polycrystalline β -Al-Mg — •Michael Feuerbacher and Marc Heggen — Institut für Festkörperforschung Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
β  −Al3Mg2 is a cubic complex metallic alloy phase with particularly large lattice constants of 28.2 Å and 1168 atoms per unit cell. The main structural elements are Friauf polyhedra arranged in fivefold coordinations. The material is potentially interesting for technological applications since it is a lightweight alloy (2.2 g/cm3) and it congruently solidifies from the melt.
We have performed uniaxial plastic deformation experiments on polycrystalline β -Al-Mg in the temperature range from 300 to 400 deg C at strain rates of 10 − 4 and 10 − 5 s − 1. The material is highly ductile and shows strong continuous work softening after the upper yield point. We have performed stress-relaxation and temperature-cycling tests to determine the thermodynamic activation parameters of the deformation process. Strongly stress dependent activation volumes in the range of 0.3 to 2.2 nm3 and a stress exponent of about 3.5 were found. The activation enthalpy assumes rather high values of 3 to 5 eV. After deformation the samples show strong shear bands oriented at 45 deg with respect to the compression axis.

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