Effect of Al2Ca Addition and Mg Content on Microstructure and Tensile Properties of Diecast Al-9Si-2Cu-Mg Alloys

Al-Si-Cu-Mg casting alloys are widely used in the automotive components because of high fluidity and high corrosion resistance. Although it is well known that the strength of Al alloys increases with increasing Mg content, the Mg content is kept under 0.3 wt% in most current Al-Si-Cu-Mg casting alloys. That is because Mg-based oxides and hard inclusions which decrease melt fluidity and mechanical properties are formed more largely during alloying and casting due to the high oxygen affinity of Mg especially in mass production on-site. In this study, the effect of Al2Ca addition and Mg content on microstructure and tensile properties of diecast Al-9Si-2Cu-Mg alloys were investigated. The ingots for high pressure diecasting were prepared from Al-9Si-2Cu with Mg master alloys containing Al2Ca for the addition of Al2Ca and high Mg in Al-9Si-2Cu. Microstructure and tensile properties of these diecast alloys were examined in comparison with those of conventional Al-9Si-2Cu-Mg alloys.