## 1 Introduction
### Foundry Alloys Al-Si
The eutectic temperature for the \(\alpha+\mathrm{Si}\) alloy is typically stated as 577 \({}^{\circ}\)C. The eutectic composition of the \(\alpha+\mathrm{Si}\) alloy is approximately 11.3% silicon by weight. However, it is important to note that different scientific literature may mention slightly different silicon concentration values for the eutectic composition. Understanding the eutectic behavior of the \(\alpha+\mathrm{Si}\) alloy is crucial for optimizing casting processes, alloy design, and the performance of aluminum-silicon-based materials [3]. The \(\alpha\)-phase in Al-Si alloys indeed refers to the solid solution of silicon in aluminum. Its maximum solubility of silicon occurs at the eutectic temperature, which is the temperature at which the alloy composition has the lowest melting point. At the eutectic composition (approximately 11.3% silicon) and temperature (around 577 \({}^{\circ}\)C), the \(\alpha\)-phase can have a maximum solubility of about 1.65% silicon. However, at lower temperatures, such as around 200 \({}^{\circ}\)C, the solubility of silicon in aluminum decreases significantly to about 0.05-0.1%. In binary Al-Si systems, the eutectic is a mixture of the \(\alpha\)-phase (aluminum-rich solid solution) and almost pure silicon. The eutectic structure consists of dark grey silicon particles distributed within a light matrix of the \(\alpha\)-phase. The amount, shape, size, and distribution of these free silicon particles in the eutectic microstructure can significantly impact the mechanical properties of the Al-Si alloy. For example, the presence of more free silicon can improve the alloy's wear resistance but may reduce its ductility. The distribution of silicon particles also affects the alloy's overall strength and toughness [28; 29]. The eutectic structure in Al-Si alloys provides several advantages such as good running capacity and reduced shrinkage, cracking, and microporosity formation. The amount, shape, size, and distribution of free silicon particles within the eutectic microstructure have a significant influence on the mechanical properties of Al-Si alloys. Additionally, the \(\alpha\)-phase, which is a solid solution of silicon in aluminum, plays an important role in the alloy's structure and mechanical behavior. Al-Si-based alloys are commonly classified based on their silicon content. The eutectic composition of the Al-Si binary system is about 11.3% Si, and alloys with Si content below or above this value are referred to as sub-eutectic or supra-eutectic, respectively. The silicon content affects the properties of the alloy, such as its mechanical strength, ductility, and machinability [30; 31]. The Al-Si-based alloys (silumin) can be classified based on their hardenability by heat treatment as follows [32; 33]:  
(a) Non-hardenable alloys, as the name suggests, cannot be hardened by heat treatment. They typically contain 5 to 20% silicon as well as other admixtures, with manganese being the most important one. The addition of manganese to silumin alloys helps eliminate the negative effects of iron impurities. Manganese acts as a scavenger, binding with iron and forming stable compounds, thereby improving the overall quality and performance of the alloy. Adding copper to silumin alloys can increase their endurance strength. Copperacts as a strengthening element, contributing to the alloy's mechanical properties. However, it is important to note that the addition of copper may slightly decrease the corrosion resistance of the alloy. Eutectic silumin alloys typically have silicon content ranging from 10% to 13%. This silicon content offers a favorable combination of foundry properties and mechanical performance. The eutectic composition ensures good casting characteristics and solidification behavior, resulting in sound and defect-free castings. The strength of silumin alloys can vary depending on the alloy composition and any additional admixtures.