The Characterization of Eutectic Al-Si Casting Alloy with Addition of Tin

Global warming and shortage of fossil fuel are the most important concerns about the need for improvement of fuel economy. While the aerospace and automotive industries still rely on steel, the drive to increase fuel efficiency and reduce CO2 emissions has led to much wider use of aluminum. Alloying aluminum with other elements like silicon helps to enhance its physical properties such as strength. Aluminum-silicon (Al-Si) alloys are the most important among casting alloys. The microstructure of Al-Si alloys is generally composed of the coarse plate-like eutectic silicon structure that makes these alloys have a fracture under tension or have a crack initiation. Therefore, the microstructure of these alloys must be modified by the addition of elements to get a fine silicon structure. This study aims to investigate the influence of tin addition on the characteristic parameters of the solidification process, microstructure, and mechanical properties of the eutectic Al-Si casting alloy. To do so, tin with different concentrations is used, and samples are taken from the base alloy and alloys modified with different tin addition. Within the study, the cooling curve of the solidification process of the samples was analyzed by using the Computer-Aided Cooling Curve Thermal Analysis (CA CCTA). Later, the microstructure of the samples was analyzed by using Optical Microscopy (OM) and Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectroscopy (SEM/EDS). Finally, the mechanical properties (hardness) of the samples were analyzed by using the Vickers hardness test. The results show that by increasing tin, the temperature of the Al-Si phase increased. When the temperature increased, the mean area of silicon particles also increased. It means that tin does not have any effect on the modification of this type of Al-Si alloy. Besides, by increasing tin, the temperature of the last solidification phase increased. The reaction temperature later was increased by the formation of intermetallic compounds. Because tin formed the intermetallic compound with aluminum and silicon. Also, hardness increasing with tin increasing was because of the solid and hard intermetallic compound formed between tin, aluminum, and silicon in the last solidification phase.