Eutectic Al–Si–Cu–Fe–Mn alloys with enhanced mechanical properties at room and elevated temperature

In this paper, we report a novel kind of eutectic Al–Si–Cu–Fe–Mn alloy with ultimate tensile strength up to 336 MPa and 144.3 MPa at room temperature and 300 °C, respectively. This kind of alloy was prepared by metal mold casting followed by T6 treatment. The microstructure is composed of eutectic and primary Si, α-Fe, Al2Cu and α-Al phases. Iron-rich phases, which were identified as BCC type of α-Fe (Al15(Fe,Mn)3Si2), exist in blocky and dendrite forms. Tiny blocky Al2Cu crystals disperse in α-Fe dendrites or at the grain boundaries of α-Al. During T6 treatment, Cu atoms aggregate from the super-saturation solid solution to form GP zones, θ″ or θ′. Further analysis found that the enhanced mechanical properties of the experimental alloy are mainly attributed to the formation of α-Fe and copper-rich phases.

► Fabricated a kind of high performance Al–Si alloy with low production costs.
► Clarified two different morphologies of α-Fe and corresponding crystal structures.
► Analyzed the crystallography of Cu-rich phases before and after T6 treatment.
► Fracture mechanism of precipitates in experimental alloys during tensile process.