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 TiSi 2 monolayer on the particles acting as nucleation sites or another poisoning mechanism not associated with TiSi 2 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.