Effects of Mn content on microstructures and mechanical properties of Al-5.0Cu-0.5Fe alloys prepared by squeeze casting

The effects of Mn content on the microstructures and mechanical properties of squeeze cast Al-5.0Cu-0.5Fe alloys at different applied pressures were examined by tensile test, optical microscopy, scanning electron microscopy and image analysis. The results show that the needle-like β-Fe phase (Al7Cu2Fe) is completely converted to the Chinese script α-Fe phase (Al15(FeMn)3(CuSi)2) when the applied pressure is 0 MPa and the Mn/Fe mass ratio reaches 1.6. As to squeeze casting, the Mn/Fe mass ratio of 0.8 is demanded for the complete conversion of β-Fe phase to α-Fe phase at the applied pressure of 75 MPa. The lower Mn content, i.e., the less Mn/Fe mass ratio, for squeeze cast alloy is due to the small size and less content of the Fe-rich phases. Excessive amount of Mn, however, deteriorates the mechanical properties because of the increase in the total amount of α-Fe and the porosity that associates with the excessive brittle phases.