Thixoextrusion of A357 aluminium alloy

The aim of this work is to attempt the application of A357 Al-Si-Mg cast alloy in the thixoextrusion process, evaluating the different parameters effect. Thixoextrusion offers several advantages compared to traditional hot-extrusion such as lower pressure, minor friction forces, higher material fluidity, longer tool life, etc. This type of semi-solid process requires high solid fractions (0.5<fs<1). Aluminium alloy A357 is a commercial cast alloy characterized by high strength, ductility and corrosion resistance. It is commonly used for cast production of automotive components and it is also suitable for semi-solid process, due to its ample range of solidification. A357 aluminium alloy has been used as a feedstock for thixoextrusion in order to investigate thixoformability at high solid fraction. Alloys with high solid fraction are less sensitive to temperature drops and allow laminar flow at higher speeds. To know the parameters that improve the mechanical properties of thixoextruded parts, some extrusion tests at constant speeds have been carried out. The results were used as the main criteria for assessing the thixoforming viability of the A357 alloy.