Forming of Etial-61 AlMgSi alloy with semi-solid metal casting technique

Etial-61 (AA6351) AlMgSi forging alloy which is widely used in automotive, aircraft and defence industry is generally formed by machining. However, semi-solid metal (SSM) processing technology enables the production of near net shape components of superior quality. With semi-solid forming processes based on billet reheating (thixocasting) increases costs significantly. To overcome this problem, a liquid-based method (rheocasting) of producing feedstock for semi-solid casting has been developed at Rio Tinto Alcan. This method called SEED (Swirled Enthalpy Equilibration Device) technology is both simple and cost-effective and involves no electromagnetic or mechanical stirring devices. The SEED process offers a short processing time and an excellent globular microstructure.In this study, semi-solid casting of Etial-61 (AA6351) AlMgSi alloy was achived with using of SEED process. In a DTA analysis concerning the solid?liquid transformation range, characterization of the Etial-61 alloy gave a liquidus temperature of 622°C and solidus temperature of 594°C, resulting in a narrow range of 28°C for the semi-solid region. The SEED process was used to produce feedstock for semi-solid forming of Etial-61 alloy. After remelted of Etial-61 alloy in a electricity heat furnace was poured into crucible on the SEED unit and alloved to swirling with 75, 80, 85, 90, 95 and 100 second times at constant rotation speed. Then, semi-solid slurry was quenched in the water at room temperature due to obtain optimum globular microstructure. It was found that 85 second swirling time produced an optimum structure having 52,4µm grain size and 0,73-0,76 shape factor. For shape forming of Etial-61 alloy, the feedstock in semi-solid state obtained with various swirling time were injected into mould which has 150°C constant temperatures at constant injection speed. The results indicated that all samples produced semi-solid casting process showed 47,6-57,8 µm cell size and 0,74-0,76 shape factor.