Improvement of Mechanical Properties of Al-Si-Mg Alloys for Sand Mold Casting in Giga-Casting Prototyping

In recent years, the monolithic integration of automotive components through giga-casting has been expected to significantly reduce man-hours and vehicle weight. However, the high cost of die modifications during the prototyping phase remains a critical challenge.

This study focuses on prototype manufacturing using low pressure sand mold casting (LPSC) facilitated by additive manufacturing processes. In LPSC, the difficulty of casting thin-walled structures is higher compared to V-HPDC for giga-casting. Furthermore, the cooling rate in sand molds is considerably slower than in giga-casting, leading to a coarse microstructure that requires heat treatment to enhance mechanical properties. However, the presence of thin-walled sections often results in significant component deformation during the water quenching stage.

While slower cooling rates mitigate deformation, they can inhibit the formation of a sufficient supersaturated solid solution, leading to sub-optimal mechanical performance. Therefore, this research aims to develop a modified AlSi7Mg0.3 alloy capable of achieving adequate mechanical properties even when subjected to air-cooling solution treatment. Plate-shaped specimens were fabricated via LPSC under various conditions, followed by forced air quenching and aging.

Subsequent tensile testing was conducted to evaluate tensile strength, 0.2% proof stress, and elongation. The results demonstrated that an AlSi7Mg0.3-based alloy with a composition of Fe: <0.1%, Mg: 0.2–0.25% and Cu: 0.5% yields superior mechanical properties, successfully balancing strength and ductility.