Rheo-Extrusion of Hypoeutectic Al-Si-Mg-Fe Alloy

Improvement of poor ductility in normally processed Al-6.7%Si-0.33%Mg-1.2%Fe alloy with coarse intermetallic compound β phases was tried by the rheo-extrusion process utilizing semi-solid slurry, which had been made by a newly developed octagonal rotor process. The obtained slurry had relatively fine solid granules and considerably smaller β phases than those of the usual castings. When rheo-extrusion tests at the constant extrusion ratio of 36 and at the ram speed of 5mm/s were carried out at various semi-solid temperatures, the round bars of 6mm diameter with smooth sound surfaces were obtained except for the tip portions in the every extrusion conditions. Microstructures of the bars consisted of relatively fine equiaxed α-Al grains, indeterminate shaped eutectic silicon and β phases. If a forced-air cooling treatment was given at the adequate position under the die out-let during rheo-extrsion, the extruded bar had an excellent tensile strength and ductility even in T6 aging condition, comparable with those of the iron-free alloy.