A study on the structural, age hardening and mechanical characteristics of Mn and Ca added Al–7Si–0.3Mg–0.6Fe alloy

The effect of Mn and Ca on the structure and properties of Al–7Si–0.3Mg–0.6Fe alloy has been investigated. Addition of Mn individually and in combination changed the morphology of platelet Fe-intermetallic compounds to Chinese script form. Ca (0.05%) refined the long platelet Fe-intermetallics and changed the morphology of platelet eutectic Si to fine fibrous form. The age hardening curve shows a double ageing peak with Mn (0.3%) and Mn + Ca additions and single hardness peak with untreated and Ca added Al–7Si–0.3Mg–0.6Fe alloys. Mn (0.3%) addition has improved the quality of the alloy (QI = 390) compared to other alloys. However, Ca has reduced the quality (QI = 296) of the alloy compared to other systems studied due to the formation of higher amount of porosity and precipitation of Al–Ca–Si intermetallics. The best combination of both tensile and impact properties has been obtained in the combined addition of Mn + Ca to Al–7Si–0.3Mg–0.6Fe alloy.