Experimental research on machinability characteristics of Al-9Si alloy: Effect of Sr and Mg additives

In this study, the effects of strontium (Sr) and magnesium (Mg) elements in certain rates added to Al-9Si alloy manufactured using permanent mold casting technique on the structural, mechanical, and machinability properties of these alloys were investigated. While microstructural images of the alloys were obtained with an optical microscope, hardness, tensile strength, and elongation to fracture were determined by conventional methods. The resultant cutting force (F) and average surface roughness (Ra) were measured as experimental outputs in the turning process. It was observed that Al-9Si alloy comprised of alpha-Al, eutectic Al-Si, beta, and primary Si phases. The addition of Sr to the Al-9Si alloy led to the formation of the Al4Sr phase and the transformation of the beta phase into the delta phase. The addition of Mg to Al-9Si-0.1Sr alloy caused the delta phase to transform into the pi phase. The hardness of the tested alloy increased significantly with the Mg addition. The yield strength and tensile strength of them increased with both Sr and Mg additions. On the other hand, elongation to fracture value of the Al-9Si alloy increased with Sr addition while it decreased with the Mg addition. The F and Ra values obtained from the Al-9Si alloy increased with Sr addition in the turning process while decreased with Mg addition. The results obtained from turning tests were discussed based on the mechanical properties of alloys