MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HYPOEUTECTIC AND HYPEREUTECTIC AL-SI CAST ALLOYS (AS CAST)

• Main Author: Kamila Raihan, Ariska
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/47133
• Institution: Institut Teknologi Bandung

Al-Si alloy is an aluminum alloy with the most widespread application. Its widespread application is due to its improved fluidity relative to the rest of aluminum cast alloys. However, the application of Al-Si cast alloy is still limited compared to Al-Si wrought alloys. Better understanding of the correlation between microstructures and mechanical properties of Al-Si cast alloys is needed to allow the wider application of this cast alloy. In this study, Al-Si casting alloy with varying silicon compositions starting from 6,5 – 19,4wt% is casted. The raw materials used for the casting processes are pure aluminum and pure silicon. The observation of microstructure, the characterization of the chemical composition of each casting product, and tensile test are done to each casting product. The results of this study show that there are ?-Al phases in the microstructure of hypereutectic alloys Al-13,1Si and Al-19,4Si. This anomaly can be caused by the built up of Si atoms in molten aluminum, which later promotes the solidification of primary Si phases in elevated temperature through nonequilibrium solidification mechanism. The occuring of nonequilibrium solidification mechanism results in the built up of Al atoms around primary Si phases. By correlating chemical composition data and microstructure with tensile strength of Al-Si, it can be shown that the tensile strength of Al-Si cast alloys not only depends on the amount of silicon in the cast alloys, but also the morphology of the eutectic phases and the primary silicon phases formed in these cast alloys. In addition to that, the presence of Fe, Cu, Mn, and Mg in Al-Si cast alloys will strengthen it through solid solution strengthening and dispersion strengthening mechanism.