The impact of Si element was investigated on the microstructure and tensile properties reliability of Al-4.5Cu-1.5Fe castings. According to the results, Si addition up to about 3 wt% increased the proportion of FeSi-rich compounds such as α-FeSi (Al8Fe3Si2) and β-FeSi (Al5FeSi) in the alloy microstructure at the expense of β-FeCu (Al7Cu2Fe) and α-FeCu (Al6(FeCu)). It also enhanced the fluidity of the alloy and lowered the porosity content of the base alloy by about 35%. The sample containing 3 wt% Si showed a maximum tensile strength of 233 ± 7 MPa and the 1 wt% Si sample displayed the highest fracture strain of 3.36% ± 0.54% compared to the values of 203 ± 10 MPa and 3.25% ± 0.60% for the base alloy. When Si was added up to 5 wt%, the formation of large volume fractions of the coarse and brittle β-FeSi platelets was promoted and tensile properties were impaired, accordingly. The Weibull analysis revealed that adding 3 wt% Si increased the reliability of tensile strength data, with the Weibull modulus being about 70% greater than the base alloy’s modulus. This sample also exhibited the highest survival probability, with an 85% higher survival probability than the base sample under a 200 MPa applied stress.
