The Effect of Iron Content on Microstructure and Mechanical Properties of A356 Cast Alloy

In the present study, microstructure and mechanical properties of A356 alloy including various amounts (0.2 to 1.2 wt pct) of iron were investigated. The alloys were produced by conventional gravity sand casting method. In order to determine the effect of iron addition to A356, optical and scanning electron microscopes (SEM/EDS) were used for microstructural examinations, and X-ray diffraction (XRD) analysis was carried out for phase characterization. Tensile tests were also conducted in order to determine effect of the Fe content on mechanical properties. It was found that as the Fe content of A356 was increased, the secondary dendrite arm spacing (SDAS) was decreased and the morphology of Al-Si eutectic became finer. From XRD examinations, different iron-based intermetallic compounds (β-Al₅FeSi and α-Al₈Fe₂Si) formations were observed. It was also observed that as iron content increased, α-Al₈Fe₂Si intermetallic was transformed into β-Al₅FeSi intermetallic. The tensile test results revealed that tensile strength and elongation values were reduced by increasing Fe content. It was also determined that β-Al₅FeSi intermetallics were more negatively effective on tensile strength than α-Al₈Fe₂Si intermetallics.