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Talks and Poster Presentations (without Proceedings-Entry):

F. Lasagni, H. Mohammadian, A. Falahati, H.P. Degischer, P. Schulz, M. Papakyriacou, B. Mingler:
"Si Precipitation Kinetics in AlSi(Mg) Alloys";
Talk: Aluminium Congress 2006, Essen, Germany; 09-21-2006 - 09-22-2006.



English abstract:
In this work, the precipitation kinetics of Si in Al-Si-base alloys is investigated in different thermal conditions and its effect on the thermal expansion is measured by dilatometry. The formation and dissolution of Si and Mg2Si precipitates is studied by means of Differential Scanning Calorimetry (DSC). Si precipitates in a diamond structure with an atomic volume 21% bigger than substitutional Si in an Al-fcc cell. Therefore, the precipitation of supersaturated Si produces an additional expansion of the alloys which can be clearly observed by dilatometry (i.e. CTE, the instantaneous coefficient of thermal expansion). Si in Al-Mg-Si alloys above the stoichiometric concentration of Mg2Si precipitates besides Mg2Si, which can be distinguished by comparing DSC thermograms with CTE(T) curves. The morphology of Si precipitates is revealed by Transmission Electron Microscopy (TEM) at different heat treatment conditions. Si precipitates mainly incoherent as platelets or in globular shape. The platelets are less stable and dissolve during heating above 300°C. The morphology of the Si precipitates and their precipitation kinetics depend strongly on the nucleation process. Nucleation is governed by the rate of heating applied to a specific initial condition produced by the previous thermal exposure and quenching rate.

Created from the Publication Database of the Vienna University of Technology.