Aluminium silicon binary phase diagram for foundry.
α: solid solution of silicon in aluminium (cfc, a =  4.04 Å);
β: solid solution of aluminium in silicon (cfc, a = 5.43 Å).
In the case of Alpax, the eutectic is shifted to 12.1 at% Si (12.5 wt%) due to the presence of sodium.
Own work
Cdang