Effects of Si and Cu contents on grain size of Al-Si-Cu alloys

The influence of the silicon and copper contents on the grain size of high-purity Al-Si, Al-Cu, and Al-Si-Cu alloys was investigated. In the Al-Si alloys, a poisoning effect was observed and a poor correlation between the grain size and growth restriction factor was obtained. A possible cause of the poisoning effect in these alloys is the formation of a TiSi2 monolayer on the particles acting as nucleation sites or another poisoning mechanism not associated with TiSi2 phase formation. In the Al-Cu alloys, a good correlation between the grain size and growth restriction factor was found, whereas in the Al-Si-Cu alloys, the correlation between these two parameters was inferior.