Extrusion of spray-formed Al-25Si-X composites and their evaluation

A comprehensive methodology to fabricate an Al-25Si-X composite via spray-forming and extrusion was investigated to judge the potential of this alloy for applications requiring high strength as well as high wear resistance and/or high elastic modulus. Billets were spray-formed with a low gas/metal ratio of about 0.8 m³/kg to reduce the consumption of nitrogen gas. The billets, having considerable porosity, were then extruded into sub-scale bars using various extrusion parameters, such as extrusion ratio, die temperature, and die configuration to optimize the extrusion conditions and eliminate the pores in the preform. Based on results obtained from the preliminary sub-scale extrusion tests, the spray-formed billets were then hot extruded into a tubular shape with outer and inner diameters of 97 mm × 77 mm, respectively, at an extrusion temperature of 500 °C. Various material properties of the extruded tubes were measured and compared with other candidate materials for these applications.