Composition: Al-6.8%Si-0.153%Fe-0.37%Mg-0.0006%Mn-0.14%Ti-0.0004%Sr.

Processing: Casting.

Etching: 10-45s immersion in 0.5% HF.

This an Al-Si hypoeutectic casting alloy with primary α-Al dendrites and an eutectic aggregate (α-Al+Si) at the interdendritic spaces. Silicon in the eutectic shows a globular/fibrous morphology due the modification with Sr. Modification improves the strength and ductility of Al-Si alloys. In this alloy, three types of intermetallics are visible:

-Needles or plates of β-AlFeSi

-Chinese-script π-AlFeSiMg

-Small Mg₂Si globules. 

Al-Si diagram

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