Microstructures and mechanical properties of squeeze cast Al–5.0Cu–0.6Mn alloys with different Fe content

Abstract

The microstructures and mechanical properties of gravity die cast and squeeze cast Al–5.0wt% Cu–0.6wt% Mn alloys with different Fe content have been studied using tensile test, optical microscope, scanning electron microscope, electron probe micro-analyzer and image analysis. The results show that four kinds of Fe-rich intermetallics may present in the final microstructures of the alloys: Chinese script α-Fe (Al15(FeMn)3(CuSi)2) and Al6(FeMn), needle-like β-Fe(Al7Cu2Fe) and Al3(FeMn) when the Fe content increases from 0.1wt% to 1.5wt%. In the gravity die cast alloy with 0.5wt% Fe, the Chinese script α-Fe presents as the main Fe-rich intermetallics, and a few needle-like β-Fe also exist. When the Fe content increases to 1.0wt%, the main Fe-rich intermetallics change to needle-like Al3(FeMn) and Chinese-script Al6(FeMn). The needle-like β-Fe disappears when the Fe content is 0.5wt% in the squeeze cast alloy with an applied pressure of 75MPa. Furthermore, the secondary dendritic arm spacing of α(Al), the percentage of porosity and the volume fraction of the second intermetallics decrease distinctly in the squeeze cast alloy compared to the gravity die cast alloy. There is a peak value of ultimate strength and yield strength for the alloy with 0.5wt% Fe. The elongations of the alloys decrease gradually with increasing Fe content and the elongation of the squeeze cast alloys is two times more than that of the gravity die cast alloys.