7075 aluminum alloy, as one of the strongest commercial alloys, has been widely used in various fields such as aerospace, mechanical manufacturing, and mold processing due to its high strength, excellent corrosion resistance, good processability, and relatively light weight. Among them, the main characteristics of the 7075 casting process determine its stability in the production process and the performance of the final product. This article will explore in detail the main characteristics of the 7075 casting process, including casting methods, alloy properties, heat treatment, and its advantages in industrial applications.

Casting method

The casting process of 7075 aluminum alloy mainly includes sand casting, metal mold casting, and low-pressure casting. Each casting method has its unique advantages and applicable scenarios.

Sand casting is one of the most traditional casting methods, suitable for producing castings with complex shapes and large sizes. Its advantage lies in its flexible process, which can produce castings of almost any shape. However, the disadvantage of sand casting is relatively low production efficiency, and the surface quality of castings may not be as good as other methods.

Metal mold casting: It is cast through metal molds and has the advantages of high production efficiency, high dimensional accuracy of castings, and good surface quality. This method is suitable for producing castings with simple shapes and high dimensional accuracy requirements. However, metal mold casting has high requirements for mold materials and casting processes, and the cost is relatively high.

Low pressure casting: It is a casting method that falls between sand casting and metal mold casting, combining the advantages of both. It uses gas pressure to press molten metal into the mold, forming castings. Low pressure casting has the characteristics of high production efficiency, low cost, and good casting quality, especially suitable for producing thin-walled castings with complex shapes and high dimensional accuracy requirements.

Alloy characteristics

7075 aluminum alloy has a high total amount of alloying elements, with a mass fraction ranging from 9.78% to 12.48%, making it one of the alloys with the highest total content of alloying elements among all series of aluminum alloys. Among them, zinc is the main alloying element. When the zinc content is in the range of 3%~7.5%, it forms MgZn2 strengthening phase with magnesium, significantly improving the tensile strength and yield strength of the alloy.

In addition, the crystallization temperature range of 7075 aluminum alloy is wide, reaching 158 ℃, which is the widest crystallization range among all series of deformed aluminum alloys. This characteristic makes 7075 aluminum alloy have a high tendency for hot and cold cracking during the casting process. Therefore, it is necessary to strictly control the chemical composition of the alloy, strengthen the purification treatment of the melt, optimize the smelting and casting process parameters in the production process to obtain good casting performance and metallurgical structure.

heat treatment

The heat treatment process of 7075 aluminum alloy is crucial for improving the mechanical properties of the material. Common heat treatment processes include solution treatment and aging treatment.

Solid solution treatment: It is to heat the alloy to a certain temperature, so that the alloy elements are fully dissolved in the matrix, forming a uniform solid solution. Subsequently, rapid cooling is carried out to preserve the solid solution state at high temperatures. Solution treatment can improve the strength and hardness of alloys, but it can reduce their plasticity and toughness.

Aging treatment: It is a process of natural aging or artificial aging for a certain period of time in the alloy after solution treatment, which causes the precipitation of second phase particles in the alloy, thereby further improving the strength and hardness of the alloy. Aging treatment can also improve the stress corrosion cracking resistance of alloys.

The heat treatment process parameters of 7075 aluminum alloy need to be adjusted according to specific product requirements and production conditions. For example, the solution treatment temperature is usually controlled between 475 ℃ and 490 ℃, and the holding time is determined based on the thickness of the casting and the alloy composition. The temperature and time for aging treatment are adjusted according to the required mechanical properties.

Advantages in industrial applications

7075 aluminum alloy has significant advantages in industrial applications due to its excellent mechanical properties and casting process characteristics.

High strength and wear resistance: The tensile strength of 7075 aluminum alloy is as high as 470-630MPa, the yield strength is 305-360MPa, and the hardness can reach HB220-250. This high strength and wear resistance make 7075 aluminum alloy an ideal material for manufacturing aircraft structural components, high stress structural components, and high-end bicycle frames.

Excellent corrosion resistance: 7075 aluminum alloy has high corrosion resistance and can resist the erosion of various acids, alkalis, salts and other media. This enables 7075 aluminum alloy to maintain good performance under harsh environmental conditions, extending the product's service life.

Good processing performance: 7075 aluminum alloy has a low melting point and good thermal conductivity, making it easy to cast and forge. Meanwhile, 7075 aluminum alloy also has good weldability, which can improve its mechanical properties through heat treatment. This makes 7075 aluminum alloy highly flexible and malleable during processing, capable of meeting various complex shape and size requirements.

Wide application fields: Due to its excellent performance characteristics, 7075 aluminum alloy has been widely used in various fields such as aerospace, mechanical manufacturing, mold processing, and high-end bicycle manufacturing. For example, in the aerospace industry, 7075 aluminum alloy is used to manufacture key structural components such as upper and lower wing panels, beams, etc; In the field of mechanical manufacturing, 7075 aluminum alloy is used to manufacture high-precision molds and fixtures; In the high-end bicycle manufacturing field, 7075 aluminum alloy is used to manufacture key components such as frames.

conclusion

In summary, the main features of the 7075 casting process include the selection of multiple casting methods, high content of alloy elements and a wide range of crystallization temperatures, precise control of the heat treatment process, and significant advantages in industrial applications. These characteristics collectively determine the stability of 7075 aluminum alloy during the production process and the performance of the final product. With the continuous advancement of technology and changes in industrial demand, 7075 aluminum alloy and its casting process will continue to play an important role in various fields, contributing to industrial development.