A Comparative Study on Microstructure and Tensile Properties of Spray Formed and Ascast Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg Alloys

In the present study, Al-28Si, Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg alloys were produced by spray forming and subsequently hot pressed for densification. The effect of alloy composition on the microstructure and mechanical behavior of spray-formed alloys were investigated. The microstructures consist of an equiaxed, nearly spheroidized grain morphology of α-Al matrix. The spray formed alloys exhibited sharply decreased segregation and increased metastable solid solubility and greater volume fraction of Si particles and intermetallic phases. Spray formed Al-28Si-5Cu-4Fe alloy contains Al 2 Cu, Al 5 FeSi along with Si. On the other hand, Al-28Si-5Cu-4Mg alloy showed Al 2 Cu, Al 48 Si 29 Mg 18 and Si. Hot pressing lead to a significant reduction of porosity and partial recrystallization of spray formed alloys. The room temperature tensile tests of spray formed hot pressed alloys showed significant increase in ultimate tensile strength compared to as cast alloys. Spray formed hot pressed Al-28Si-5Cu-4Fe alloy exhibited superior ultimate tensile strength and significant increase in elongation to fracture. This may be attributed to the presence of homogeneous distribution of fine Si particles, high content of short needle-like β-Al 5 FeSi intermetallic and precipitation strengthening phases.