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Talks and Poster Presentations (without Proceedings-Entry):

R. Koos, G. Requena, E. Boller:
"Thermo-mechanical behaviour and internal architecture of near-eutectic and hypereutectic Al-Si alloys";
Talk: LightMAT 2013, Bremen; 09-03-2013 - 09-05-2013.



English abstract:
The three-dimensional (3D) architecture of near-eutectic AlSi10Cu6MgNi2 and AlSi12Cu5MgNi2 alloys and that of a hypereutectic AlSi17Cu4Mg alloy is studied as a function of solution treatment (ST) time at 500° C by synchrotron microtomography using absorption and phase contrast imaging. The alloys are formed by eutectic plus primary Si and aluminides embedded in an Alpha-Al matrix. The rigid phases (Si and aluminides) in as-cast condition with an amount of ~ 25vol% form a highly interconnected network able to carry load and, thus, contribute to the strength of the alloys. The evolution of the volume fraction, interconnectivity, contiguity and morphology of phases is quantified from tomographies of the same sample in as-cast condition, after 1h and 4h ST for each alloy. The AlSi17Cu4Mg alloy shows a decrease in the volume fraction of aluminides from ~ 6vol% to 4vol% after 4h ST owing to the partial dissolution of Al2Cu segregated during solidification. Furthermore, the interconnectivity of the aluminides network (estimated as the volume fraction of the largest particle with respect to the total volume fraction of aluminides) in this alloy decreases from ~ 90% to ~ 70%. These parameters remain practically constant for the AlSi10Cu6MgNi2 and AlSi12Cu5MgNi2 alloys, which present ~ 10vol% of aluminides with ~ 95% interconnectivity. The eutectic and primary Si can only be revealed by phase contrast due to the similar attenuation with respect to the Alpha-Al matrix. It presents a large contiguity with the aluminides network, especially for the AlSi10Cu6MgNi2 and AlSi12Cu5MgNi2 alloys, which results in a high morphological stability during the solution heat treatments The tomographic results are correlated with the high temperature strength (300°C and 380°C) and the thermal cycling creep resistance of the alloys after the same ST times aiming at identifying the microstructural parameters responsible for their behaviour.

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