Microstructure and mechanical properties of an Al–12.7Si–0.7Mg alloy processed by extrusion and heat treatment

Direct chill (DC) cast Al–12.7Si–0.7Mg alloy without chemical modification was hot extruded and subsequently heat-treated under various conditions. The microstructure and tensile properties of the extruded profile were investigated aiming at understanding the strengthening mechanisms. The results show that the refined microstructure characterized by fine Si particles uniformly distributed in the Al matrix of fine equiaxed grains was promoted by hot extrusion. The alloy after T6 treatment exhibits good ductility and much higher proof strength as well as tensile strength compared to 6063 alloy in general. The strengthening was attributed to be the combining effect of particle, grain boundary and precipitation strengthening.

Research highlights
► Direct chill cast Al–12.7Si–0.7Mg billet was generated with fibrous eutectic Si.
► Direct chill cast Al–Si alloys without chemical modification could be hot-deformed.
► The Mg bearing wrought Al–Si alloys exhibit superior mechanical properties.