  In this work, we studied the effect of Si on the microstructure and tensile
properties of the as-cast Al-5.0Cu-0.6Mn-1.2Fe alloys which were produced by
casting with or without applied pressure. The results show that the addition of
Si can significantly influence the microstructure and tensile properties of the
alloys. For the alloys produced without pressure, the addition of Si can
promote the formation of Chinese script {\alpha}-Fe, suppress the precipitation
of plate-like Al3(FeMn) and Chinese script Al6(FeMn) and increase the volume
percent of porosity, resulting in a remarkable decrease in the ultimate tensile
strength (UTS) and yield strength (YS). For the alloys produced with a pressure
of 75 MPa, the addition of Si can also promote the formation of fine Chinese
script {\alpha}-Fe and high number density Al2Cu ({\theta}) phases, resulting
in a slight increase in UTS and YS. The strength and elongation of the alloys
increases with increasing applied pressure at the same Si level, which are
attributed to the elimination of porosity, grain refinement strengthening and
solid-solution strengthening. The alloy with addition of 1.1 % Si produced
under the applied pressure of 75 MPa shows the best tensile properties, where
the UTS, YS and elongation is 237 MPa, 140 MPa and 9.8%, respectively.
