The present study shows a new manufacturing process of foams of Al alloys by the modification of the conventional solution heat treatment of three alloys Al-6Si-3Cu-xMg (x=7, 9 and 11wt%). Over-heating the alloys during 6h at 520, 560 and 600°C allowed to obtain foams with maxima porosities of 40% and pore sizes from 20 to 150µm, originated due to the localized melting of second phases. The characteristics of the foams highly depended on the Mg content and the heat treatment temperature.