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F. Lasagni, A. Lasagni, C. Holzapfel, F. Mücklich, H.P. Degischer:
"Three Dimensional Characterization of Unmodified and Sr-Modified Al-Si Eutectics by FIB and FIB EDX Tomography";
Advanced Materials, 8 (2006), 8; 719 - 723.

he excellent castability and mechanical properties of AlSi-alloys make them popular foundry alloys. These alloys can be modified and/or heat-treated to improve their ductility. Al-Si alloys present a simple binary system with an eutectic point close to 12.5 wt.% Si. There is an important limitation in the solubility of Si by only 1.65 wt.% at the eutectic temperature of about 577 °C. The morphology of these alloys depends strongly on the Si content as well as the casting process. As cast alloys contain dendritic a-grains with an eutectic structure in-between formed by lamellar Si separated by the a-phase. The Si forms initially a percolating network of a few lm width between the dendritic arms of primary a-Al consisting of several thin (~1-2 µm) lamellae. The addition of Sr or Na (0.01-0.03 wt.%) modifies the eutectic morphology into a fibrous network improving both ductility and tensile strength of the alloy.

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC06587230