  The effect of Si on Fe-rich intermetallics formation and mechanical
properties of heat-treated squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy was
investigated. Our results show that increasing Si content promotes the
formation of Al15(FeMn)3(SiCu)2 (${\alpha}$-Fe), and varying the morphology of
T (Al20Cu3Mn2) where the size decreases and the amount increases. The major
reason is that Si promotes heterogeneous nucleation of the intermetallics
leading to finer precipitates. Si addition significantly enhances ultimate
tensile strength and yield strength of the alloys. The strengthening effect is
mainly owing to the dispersoid strengthening by increasing volume fraction of T
phase and less harmful ${\alpha}$-Fe with a compact structure, which make the
cracks more difficult to initiate and propagation during tensile test. The
squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy with 1.1% Si shows significantly
improved mechanical properties than the alloy without Si addition, which has
tensile strength of 386 MPa, yield strength of 280 MPa and elongation of 8.6%.
