The Microstructure of AlSi9Cu3 Alloy after Different Stages of Liquid Metal Preparation

Aluminium alloys are one of the most important casting alloys. Among them, the Al-Si alloys comprise perhaps the most important group – about 80% of the aluminium casts are made of them. These materials are characterized by a very good technological properties, good corrosion resistance and tribological properties. Their main disadvantage is, however, presence of the massive, brittle silicon crystals. They significantly affect alloys mechanical properties. Liquid metal treatment is essential for modification of Al-Si eutectic structure. The following work presents results of the research on the microstructure of the AlSi9Cu3 alloy after different stages of liquid metal preparation. Three casting processes have been conducted, chemical composition of the material in each case was in agreement with EN 1706 specification. During each casting process, three specimens were gravity cast: first, made from pure ingots; second, after the scrap addition and third one after the liquid metal treatment. Qualitative and quantitative evaluation of the microstructure was done on each specimen. Specimens cast from pure ingots are characterized by a refined Al-Si eutectic microstructure. After scrap addition, the silicon crystals became morphology of the massive platelets. What is more, intermetallic phases observed within the structure posses different morphologies after different stages of liquid metal preparation. After scrap addition, increased gas porosity was observed. Liquid metal treatment reduced slightly the formation of gas pores