Effect of Silicon on Machinability in AlSi6, AlSi12 and AlSi18 Alloys

In this study, Al-Si alloys containing 6%, 12%, and 18% silicon by weight were produced using the permanent mold casting method. The samples were examined microstructurally, hardness and tensile tests were conducted. Furthermore, the machinability characteristics of the samples were investigated. The findings showed that the silicon added to aluminum has a significant impact on microstructure, mechanical properties, and machinability. The addition of silicon to aluminum up to 12% by weight increases the amount of Al-Si eutectic in the microstructure. However, unlike other samples, primary silicon particles were detected in the microstructure of the composition containing 18% Si by weight. Also, both hardness and tensile strength increased with the increasing silicon content. However, with the increasing silicon ratio, the ductility of the material and the thrust force during the drilling process decreased. The highest thrust force (961 N) occurred at 6% Si additive ratio (Al6Si) and at a rotational speed of 2500 rpm. Burr formation was observed at the hole exit in 6% Si additive ratio and 12% Si additive ratio. The surface roughness occurring inside the holes increased with the increasing silicon ratio. Graphical Abstract