Effect of magnesium (Mg) content and artificial aging on microstructure and mechanical properties of homogenized Al-Si-Cu alloy

• Main Author: Zulkifli, Mohd Faizal
• Format: Thesis
• Language: English; English
• Published: 2024
• Subjects: T Technology (General); TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.utem.edu.my/id/eprint/28417/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=124288

The study of the effect of magnesium (Mg) content and artificial aging on the microstructure and mechanical properties of homogenized Al-Si-Cu alloys was critical for advancing the development of lightweight, high-strength materials for automotive and aerospace applications. Several studies on the modification and addition of alloying elements conducted previously reported positive improvements to enhance the mechanical properties of Al-Si-Cu alloys, including the addition of Magnesium (Mg) content, Copper (Cu), Silicon (Si), and other alloying elements. However, there was a lack of technical data that correlated both the effect of magnesium added and artificial aging as T6 Heat treatment into Al-Si-Cu alloy. Despite extensive research on Al-Si-Cu alloys, the specific impact of varying Mg concentrations on their homogenized microstructure and resultant mechanical properties remained inadequately understood. This research aimed to fill this gap by systematically investigating the influence of 0.5%wt, 0.8%wt, and 1.2%wt of Magnesium (Mg) contents on A356 alloys under 1, 3, and 5 hours of artificial aging after casting through permanent mold casting and thixoforming process. To achieve the project objectives, nine (9) combination of Taguchi method runs for A356 alloy samples with varying Mg concentrations and different artificial aging were prepared through Permanent Mold and Thixoforming casting process. As a results, the microstructural characteristics were analyzed using Optical microscopy (OM), Scanning electron microscopy (SEM) incuding energy-dispersive X-ray spectroscopy (EDS) for elemental mapping for specific area. Hence, a mechanical properties evaluation was performed, including tensile strength (E8M) and Vicker microhardness (E92), through standardized ASTM testing procedures. The results revealed that increasing Mg content significantly refined the microstructure, enhancing the dispersion of secondary phases and reducing the size of primary Si particles. This refinement of microstructure led to notable improvements in mechanical properties. Specifically, alloys with higher Mg content exhibited increased yield strength (YS) and ultimate tensile strength (UTS) while reducing the elongation to fractures. In addition, artificial aging also tends to increase yield strength (YS) and ultimate tensile strength (UTS). Other than that, the hardness results show an increasing trend with a longer artificial aging period while reducing Vickers Hardness (HV) value under the influence of the increment of Mg addition into the alloying system. These findings highlighted the critical role of Mg and artificial aging in optimizing the performance of Al-Si- Cu alloys and provided valuable insights for their application in high-performance engineering components. This study not only elucidated the relationship between Mg content and the microstructure-mechanical property interplay in homogenized Al-Si-Cu alloys but also offered a pathway for designing advanced materials with superior properties for industrial applications.