As a part of on-going research on phase transformations during the deformation of light alloys, the effect of silicon excess on the extrudability and mechanical properties of the standard AlMgSi1 alloy within AA6082 alloy is investigated in this study. The AlMgSi1 alloy and three experimental aluminum alloys with a silicon content of 1.98%, 3.73% and 5.51% were direct-chilled cast into billets 95 mm in diameter, homogenized at 540 °C for 4 h and extruded into 12 mm diameter rods at different extrusion speeds. The results showed that an increase in the silicon content reduced the extrudability of the AlMgSi1 alloy by lowering the limiting extrusion speed. However, the extruded alloys with 3.73% and 5.51% silicon, generally characterized by a fine grained microstructure, exhibited higher strength levels compared with the 1.98% silicon alloy. Nonetheless, the mechanical properties of these alloys, in the T6 temper condition, were below those of the AlMgSi1 base alloy.