Ductility and solidification issues in Al-Si-Cu-Mg alloys

The challenge in using the secondary metal when producing the alloy is, the high level of Fe impurity causes detrimental effect on mechanical properties and microstructures; High level of Fe produces long and needle-like brittle intermetallic phase particles. This happened at the early stage of the solidification and hence it blocks the feeding mechanism during casting as well. Increasing the Si level to about 9 w.t.% to these alloys reduces the detrimental effect of Fe by producing fine intermetallic particles in the microstructure. The mechanism responsible for the beneficial effect of the high Si, in these alloys will be discussed.