In the aluminum alloy family, the 7000 series aluminum alloys occupy a pivotal position due to their superior strength properties, often referred to as "synonymous with high-strength aluminum alloys."
7075 aluminium and 7050 aluminum, as two star materials in this series, are frequently compared. Both belong to the aluminum-zinc-magnesium-copper alloy family, but subtle adjustments to their composition create unique performance advantages, leading to drastically different applications.
The core alloying elements of both 7075 and 7050 aluminum are zinc, magnesium, and copper, but slight adjustments to their proportions have a butterfly effect on the final material properties.
7075 aluminum plate has a relatively higher zinc content, typically between 5.1% and 6.1%, a copper content of approximately 1.2% to 2.0%, and a magnesium content of 2.1% to 2.9%. This composition allows it to form a large number of strengthening phases after quenching and aging, laying the foundation for its high strength.
7050 aluminum, on the other hand, features an optimized composition with a slightly lower zinc content (5.7%-6.7%) and an increased copper content of 1.8%-2.3%, while strictly controlling the content of impurities such as iron and silicon (typically below 0.15%). This adjustment not only enhances the alloy's toughness but also significantly improves its resistance to stress corrosion, a key reason for its popularity in the aerospace field.
In terms of room temperature strength, 7075 aluminum is undoubtedly the strongest among its peers. After T6 heat treatment, its tensile strength reaches 572 MPa, and its yield strength is as high as 503 MPa. Such strength levels are extremely outstanding among aluminum alloys, even comparable to some steels.
In comparison, 7050 aluminum has slightly lower room temperature strength; its tensile strength in the T7451 heat-treated state is approximately 517 MPa, and its yield strength is approximately 455 MPa.
However, it is worth noting that 7050 aluminum's advantages lie in its high-temperature strength and fatigue strength. In high-temperature environments of 120℃-150℃, 7050 aluminum exhibits higher strength retention and is less prone to plastic deformation; while 7075 aluminum shows relatively significant strength degradation at high temperatures. Simultaneously, 7050 aluminum has a longer fatigue life and can better withstand repeated alternating loads, which is crucial for fields with extremely high reliability requirements, such as aerospace.
High strength often comes with reduced toughness, and 7075 aluminum is no exception. Its fracture toughness is relatively low, making it prone to brittle fracture under severe impact, which limits its application in impact-load scenarios to some extent.
In contrast, 7050 aluminum, through optimized composition and heat treatment processes, significantly improves fracture toughness while maintaining high strength, resulting in stronger impact resistance.
The difference in corrosion resistance is even more pronounced. Due to its higher copper content and relatively lax control of impurities, 7075 aluminum is prone to stress corrosion cracking and intergranular corrosion, especially in humid, salt spray environments, where corrosion problems are more severe. Therefore, surface anti-corrosion treatments such as anodizing and painting are usually required before use.
7050 alloy, through strict control of impurity content and the use of special heat treatment processes (such as T7451), significantly improves its resistance to stress corrosion and intergranular corrosion, exhibiting superior stability in harsh environments and meeting the requirements of some demanding working conditions without complex surface treatments.
7075 aluminum has certain machinability in the annealed state, allowing for cutting and stamping. However, after heat treatment strengthening, its hardness increases significantly, increasing the difficulty of machining and causing faster tool wear, requiring the use of specialized tools and appropriate machining parameters.
7050 aluminum, on the other hand, has relatively better machinability, especially in the T7451 state, where its cutting performance is excellent, resulting in higher surface quality and making it suitable for manufacturing complex, high-precision parts.
However, 7050 aluminum has relatively poor weldability, prone to cracking during welding, requiring special welding processes and welding materials. 7075 aluminum also has poor weldability, but preheating and post-weld heat treatment can improve weld quality to some extent.
With its exceptional room-temperature strength, 7075 aluminum plate is widely used in industrial and civilian applications where high strength is required. In the aerospace industry, it is commonly used to manufacture secondary load-bearing structures for aircraft, such as landing gear doors, wing ribs, and fuselage frames. In the space industry, it can be used to manufacture rocket engine supports and satellite structural components.
In the civilian sector, 7075 aluminum is also ubiquitous. Sports equipment is a significant application, including bicycle frames, trekking poles, and ski bindings. These products require sufficient strength while maintaining lightweight construction, a requirement that 7075 aluminum perfectly meets.
Furthermore, in mold manufacturing, 7075 aluminum can be used to manufacture mold frames and templates for small and medium-sized molds. In the medical device industry, it can be used to manufacture surgical instruments and rehabilitation equipment.
7050 aluminum, with its excellent high-temperature strength, fatigue strength, corrosion resistance, and toughness, has become a favorite in the aerospace industry, primarily used to manufacture the main load-bearing structures of aircraft. For example, key components of large passenger aircraft, such as wing skin, wing spars, and fuselage stringers, are mostly made of 7050 aluminum. These components not only need to withstand enormous loads but also maintain long-term stability in the complex environment of high altitudes.
In the aerospace field, 7050 aluminum can be used to manufacture the rocket body structure and the main load-bearing frame of satellites. In the defense field, it can be used to manufacture the protective plates of armored vehicles and missile body components.
Furthermore, in the petrochemical industry, 7050 aluminum can also be used to manufacture high-pressure vessels and pipelines, ensuring the safe operation of equipment in high-temperature, high-pressure corrosive environments due to its excellent corrosion resistance and strength.
Original Source:https://www.aircraftaluminium.com/a/7075-vs-7050-aluminum-alloy.html
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