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What is 7075 Aluminum Alloy

Posted by: die casting 2023-11-09 Comments Off on What is 7075 Aluminum Alloy

7075 aluminum alloy is a high-strength material commonly used in aerospace applications. It is known for its excellent strength-to-weight ratio and good corrosion resistance. The alloy primarily consists of zinc as the major alloying element, along with small amounts of copper, magnesium, and chromium.

Due to its high strength and low density,  aluminum 7075 is often used in the production of aircraft structures, including fuselage components and wings. It’s also employed in the manufacturing of high-performance bicycles, rock climbing equipment, and certain firearm components.

The alloy has good machinability and heat treatability, making it suitable for various applications where strength and lightness are crucial. Keep in mind that while it has many advantages, 7075 aluminum can be more susceptible to corrosion compared to other aluminum alloys, so protective coatings or surface treatments may be applied in certain cases.

The main alloying elements in 7075 aluminum alloy are:

  1. Zinc (Zn): The primary alloying element in 7075, contributing to the alloy’s high strength and hardness.
  2. Copper (Cu): Copper is added to enhance the alloy’s strength and improve corrosion resistance.
  3. Magnesium (Mg): Magnesium is another key element that contributes to the alloy’s strength and makes it heat-treatable.
  4. Chromium (Cr): Chromium is often present in small amounts to improve the alloy’s resistance to corrosion.

The 7 Series Aluminum Alloys

Here are some key members of the 7 series aluminum alloys:

  1. 7075 Aluminum Alloy: Known for its high strength and used in aerospace applications, including aircraft structures and components.
  2. 7050 Aluminum Alloy: Similar to 7075 but with improved toughness. Commonly used in aerospace applications, such as aircraft landing gear.
  3. 7475 Aluminum Alloy: Known for its high strength and corrosion resistance. Used in aerospace applications, particularly in the construction of aircraft wings.

Physical and Mechanical Properties

Here are some general physical and mechanical properties of nickel alloy in718:

Physical Properties:

  1. Density: 2.78 g/cm³ (173.9 lb/ft³)
  2. Melting Point: 477-635°C (890-1175°F)
  3. Thermal Conductivity: 130 W/(m·K)
  4. Electrical Conductivity: 33.6–37.7 MS/m

Mechanical Properties:

  1. Tensile Strength: 470-560 MPa (68,000-81,000 psi)
  2. Yield Strength: 390-500 MPa (56,500-72,500 psi)
  3. Elongation at Break: 5-12%
  4. Hardness (Brinell): 150-190 HB

Other Properties:

  1. Modulus of Elasticity: 71 GPa (10,300 ksi)
  2. Poisson’s Ratio: 0.33
  3. Fatigue Strength: 160 MPa (23,000 psi) for 500 million cycles

Chemical Composition

The chemical composition of 7075 aluminum alloy typically includes the following major elements:

  1. Aluminum (Al): The primary element, making up the majority of the alloy.
  2. Zinc (Zn): The main alloying element, contributing to the alloy’s high strength.
  3. Copper (Cu): Enhances strength and provides corrosion resistance.
  4. Magnesium (Mg): Adds strength and makes the alloy heat-treatable.
  5. Chromium (Cr): Present in smaller amounts to improve corrosion resistance.
  6. Other Trace Elements: There may be trace amounts of other elements depending on the specific alloy and manufacturing process.

The specific composition can vary slightly based on the manufacturing standards and the desired properties of the alloy. Here’s a rough range of composition for 7075 aluminum:

  • Aluminum (Al): 87.1-91.4%
  • Zinc (Zn): 5.1-6.1%
  • Copper (Cu): 1.2-2.0%
  • Magnesium (Mg): 2.1-2.9%
  • Chromium (Cr): 0.18-0.28%

Key Features of 7075 Aluminum Alloy

The key features of 7075 aluminum alloy include:

  1. High Strength: 7075 is known for its exceptional strength, making it one of the strongest aluminum alloys available. It has a high tensile strength and good toughness.
  2. Lightweight: Despite its high strength, 7075 aluminum is relatively lightweight, making it an excellent choice for applications where weight is a critical factor, such as in aerospace.
  3. Heat-Treatable: 7075 is a heat-treatable alloy, meaning it can be strengthened through heat treatment processes, such as solution heat treatment and aging. This allows for tailoring the material’s properties to specific applications.
  4. Good Machinability: While it can be more challenging to machine compared to some other aluminum alloys, 7075 still has good machinability, allowing for the production of intricate parts.
  5. Corrosion Resistance: It offers good corrosion resistance, especially when compared to other high-strength aluminum alloys. However, it may not be as corrosion-resistant as some other aluminum alloys.
  6. Applications in Aerospace: Due to its combination of high strength and low weight, 7075 is widely used in aerospace applications, including aircraft structures, fuselage components, and wings.
  7. Military and Defense Applications: The alloy is also used in military and defense applications for its strength and durability.
  8. High Stress and Fatigue Resistance: 7075 exhibits high stress and fatigue resistance, making it suitable for components that undergo significant loads or cycles.
  9. Limited Weldability: While 7075 can be welded, it is not as easily welded as some other titanium alloy ti64. Special considerations and techniques are often required for welding.

Applications of 7075 Aluminum Alloy

Some common applications include:

  1. Aerospace Components: 7075 is extensively used in the aerospace industry for manufacturing aircraft structures, including fuselage components, wings, and other critical parts. Its high strength and low weight contribute to fuel efficiency and overall performance.
  2. Military and Defense Equipment: The alloy’s strength and durability make it suitable for military and defense applications, such as the production of armored vehicles, missile components, and other high-stress parts.
  3. High-Performance Bicycles: 7075 is employed in the construction of high-end bicycle frames and components. The alloy’s lightweight nature and strength are valued in the cycling industry.
  4. Rock Climbing Equipment: Components like carabiners and other climbing gear benefit from the strength and toughness of 7075 aluminum.
  5. Firearm Components: Some firearm manufacturers use 7075 aluminum for certain gun components due to its strength and resistance to wear and tear.
  6. Automotive Components: In some cases, 7075 is used in the automotive industry for specific high-performance applications, such as suspension components and parts where lightweight strength is crucial.
  7. Machined Parts: Its good machinability makes 7075 suitable for the production of precision-machined parts in various industries.
  8. Sports Equipment: The alloy is employed in the manufacturing of sports equipment, including high-performance car parts and certain elements of sports gear.
  9. Marine Components: While not as corrosion-resistant as some other stainless steel alloy 303, 7075 can still be used in marine applications where its strength is a critical factor.

Mechanical Performance

The mechanical performance of 7075 aluminum alloy is notable for its high strength and toughness. Here are some key aspects of its mechanical properties:

  1. Tensile Strength: 7075 aluminum alloy exhibits a high tensile strength, typically ranging from 470 to 560 MPa (68,000 to 81,000 psi). This makes it one of the strongest aluminum alloys.
  2. Yield Strength: The yield strength of 7075 is in the range of 390 to 500 MPa (56,500 to 72,500 psi). Yield strength is the point at which the material begins to deform plastically.
  3. Elongation at Break: The percentage of elongation at break for 7075 aluminum alloy is typically between 5% and 12%. This represents the amount by which the material can stretch before breaking.
  4. Hardness (Brinell): The Brinell hardness of 7075 aluminum alloy falls in the range of 150 to 190 HB, indicating its resistance to indentation or abrasion.
  5. Modulus of Elasticity: The modulus of elasticity, which measures the stiffness of the material, is approximately 71 GPa (10,300 ksi) for 7075 aluminum.
  6. Fatigue Strength: The fatigue strength of 7075 aluminum alloy is around 160 MPa (23,000 psi) for 500 million cycles. Fatigue strength is crucial in applications involving repeated loading and unloading.

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