An investigation of casting properties of magnesium alloys

In this study, surface active (Sn, Pb), non-surface active (Si, Fe, Cu) and nucleant (Zr, Ti) elements have been added to AZ91 magnesium alloy in the ranges between 0,5-2 wt. % aiming to develop its casting properties that is used in automotive, aerospace and defence industry. Effect of argon and CO2+SF6 gases and mould temperature on casting practice have been investigated as well as effect of added elements on fluidity, hot tearing and mechanical properties. A brief discussion has also been made on microstructural evaluations. Results showed that casting practice was better as the melting carried out under argon atmosphere while the mould atmosphere was CO2+SF6 gas. Fluidity has been increased with increasing mould temperature and additions of Sn, Pb and Cu to the alloy. On the other hand, additions of Si, Fe and Ti reduced the fluidity whereas Zr did not alter it. It was observed that Fe, Zr and Ti increased hot tearing the most amongs the other elements used. Additions of Sn, Pb, Si, Fe, Cu, Zr and Ti had benefical effect on tensile strength in lower concentrations while their effect is educed at higher concentrations except Si. At lower concentartions Pb resulted in higher elongation while Sn, Fe and Ti reduced it. At higher concentrations (2 wt %), Si has improved both hardness and elongation while Sn, Pb, Fe, Cu, Zr and Ti detoriated both hardness and elongation.