Dresden 2003 – wissenschaftliches Programm

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M: Metallphysik

M 6: Symposium: Phasenumwandlungen in Schmelzen IV

M 6.3: Vortrag

Montag, 24. März 2003, 17:00–17:15, IFW A

Eutectic growth in directionally solidified ternary Ag-Cu-Zn alloys — •Anne Drevermann, Victor Witusiewicz, Ulrike Hecht, and Stephan Rex — ACCESS e.V., Intzestr. 5, 52072 Aachen

Samples of two different compositions near the ternary eutectic point at 57.6 wt.% Ag, 23.0 wt.% Zn and 19.4 wt.% Cu were directionally solidified using a high gradient Bridgman furnace. By means of varying the solidification rate dendritic, cellular and planar morphologies were generated. The metallographically prepared samples were analysed with light-optical and backscattered electron microscopy for structure formation. EDX was used to determine the chemical compositions of the three phases α-Ag, α-Cu and β-Zn at different stages of coupled growth and of the quenched liquid ahead of the solid/liquid interface.

To support the experimental work the thermodynamic database of Ag-Cu-Zn was re-elaborated via measurements and the CALPHAD method, resulting in a reliable description of the entire system with the possibility to calculate phase equilibria, the liquidus projection of Ag-Cu-Zn, etc. The thermodynamic description allowed for understanding the phase (trans-)formations and the volume fractions of the complex three-phase patterns formed in the directionally solidified samples.