Microstructure and mechanical properties of extruded Al-Si alloy (A356) in the semi-solid state

Smooth round bars were produced from conventional non-modified cast alloy, A356, by semi-solid extrusion after isothermal holding in mushy zone. Extrusion process was carried out in an apparatus, designed and prepared for this purpose at a ram speed, 2.5 mm/s. Three forming temperatures: 560, 570 and 580 degrees C; three isothermal holding times: 5, 30 and 60 min; and two extrusion reduction ratios: 5.3 and 17.8 were the used parameters. A clear modification of eutectic phase and an improvement in hardness and tensile properties were found compared with those of conventional casting. The tensile test specimens fracture surfaces were examined using SEM. Furthermore, wear resistance, fatigue strength and impact energy were also, improved significantly. (C) 2008 Elsevier Ltd. All rights reserved.