Aluminium-silicon alloy has found extensive use in the automotive and aerospace industries due to its excellent castability, good thermal conductivity, low expansion coefficient and good corrosion resistance. This project was undertaken to analyze the effect of silicon morphology on machinability when turning Al-Si-Cu-Mg alloy by PVD TiN coated insert. Various cutting speeds and feed rates were employed. The process was performed under dry cutting condition. Experiments revealed that surface roughness improved when cutting speed increased from 70 m/min to 250 m/min for all machining conditions. The results show that The workpiece containing Sb have the highest surface roughness value and highest cutting force in the most of cutting conditions with high ductility.The study also revealed that cutting force increased when feed rate was increased from 0.5 mm/rev to 0.15 mm/rev.The study should be especially useful to use some elements in casting process that are suitable to achieve the best surface roughness in machining process.