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Hypo-eutectic Al-Si alloys (Al-Si alloys other than eutectic and hyper-eutectic): The Si content of hypo-eutectic Al-Si alloys commonly used in industry is generally 6% to 8%, and other strengthening elements are added for toughness processing. Common ones are Al-Si-Mg alloys and Al-Si-Cu alloys. Among them, Al-Si-Mg alloys mainly use the Mg2Si phase formed by Mg and Si as the strengthening phase, and Al-Si-Cu alloys mainly use the Mg2Si phase formed by Mg and Si as the strengthening phase. The high solid solubility of Cu in α-Al produces solid solution strengthening and dispersion strengthening of the Al2Cu strengthening phase precipitated during heat treatment.

Aluminum alloy is a general term for aluminum-based alloys. The main alloying elements are copper, silicon, magnesium, zinc, manganese, and the minor alloying elements are nickel, iron, titanium, chromium, lithium, etc. The most widely used non-ferrous metal structural materials in the industry have been widely used in aviation, aerospace, automobile, machinery manufacturing, shipbuilding and chemical industries.

1. Melting and casting method
The smelting and casting method has simple equipment, low cost and can realize large-scale industrial production. It is the most extensive preparation method of alloy materials. Using conventionally cast high-silicon aluminum alloys, the distribution of Si is extremely uneven, cracks are prone to occur during processing, and the material has severe component segregation, coarse grains, and poor mechanical properties. It is difficult to carry out subsequent processing such as machining. As the silicon content in the alloy increases, the problem becomes more prominent, so it is difficult to prepare high-silicon aluminum alloy materials by conventional casting.
2. Infiltration method
The infiltration method is divided into pressure infiltration method and pressureless infiltration method. The pressure infiltration method is to pressurize the base metal melt into the reinforcement gap by mechanical pressure or compressed gas, which can solve the problem of incomplete infiltration due to the non-wetting of the reinforcement material and the metal liquid, but the pressure system is relatively complex. , thus restricting its application development
3. Powder metallurgy
The main process of powder metallurgy is to uniformly disperse a certain proportion of aluminum powder, silicon powder and binder, mix the powder by dry pressing, injection and other methods, and finally sinter in a protective atmosphere to form a relatively dense material. This method solves the problem of poor wettability between silicon particles and aluminum matrix, and it is difficult for silicon particles to be added into the melt, and the material can be formed at one time with less cutting process, which overcomes the disadvantage that metal matrix composite materials are difficult to process. However, this method is complicated in process, difficult to precisely control, not compact, and high in cost.
4. Vacuum hot pressing
The vacuum hot pressing method refers to a sintering process in which pressure molding and pressure sintering are carried out at the same time. The general process is: under vacuum conditions, the powder is installed in the mold cavity, and the powder is heated while pressurizing, and a compact and uniform material is formed after a short time of pressurization. However, due to the complex process and poor operability, the application of this technology in the preparation of high-silicon aluminum alloys is limited.
5. Rapid cooling/jet deposition
Rapid cooling/spray deposition technology is a rapid solidification technology developed to compete with powder metallurgy and other technologies in order to overcome the problems of complex procedures and serious oxidation. Because this process has incomparable advantages over other processes, it has developed rapidly in recent years. Rapid cooling/spray deposition has the following advantages: 1) no macrosegregation; 2) fine and uniform equiaxed microstructure; 3) fine primary precipitates; 4) low oxygen content; 5) improved hot workability.