7075 T76 Aluminum
7075 T76 aluminum is a high-strength deformed aluminum alloy based on 7075 aluminum alloy, treated in the T76 heat treatment state. It is an Al-Zn-Mg-Cu system super hard aluminum, specifically designed to improve stress corrosion resistance.
7075 T76 is a high-strength aluminum alloy in the 7000 series, known for its excellent mechanical properties and enhanced corrosion resistance due to a specific heat treatment process.
7075 T76 aluminum is a high-performance, heat-treatable aluminum alloy in the 7000 series, with zinc as the primary alloying element. It has the same basic chemical composition as other 7075 alloys—typically containing about 5.1-6.1% zinc, 2.1-2.9% magnesium, 1.2-2.0% copper, along with trace amounts of chromium, manganese, silicon, and titanium—but is renowned for its specific T76 state.
7075 T76 State Characteristics
- Heat treatment process: The T76 state is based on T6 (solution heat treatment + artificial aging) with the addition of over-aging treatment, which improves stress corrosion cracking resistance through a two-step aging process.
- Performance balance: Compared to the T6 state, T76 has slightly lower strength but significantly improved stress corrosion and exfoliation corrosion resistance.
7075-T76 Aluminum Composition
- Aluminum (Al): Balance
- Zinc (Zn): 5.1–6.1%
- Magnesium (Mg): 2.1–2.9%
- Copper (Cu): 1.2–2.0%
- Other Elements: Trace amounts of chromium, manganese, silicon, and titanium
7075 alloy is known for its excellent strength-to-weight ratio. Especially in the T76 state, which is achieved by over-aging the alloy after the typical T6 heat treatment process. This additional treatment reduces residual stress, improves fatigue strength, and enhances stress corrosion cracking resistance, making it particularly suitable for critical high-stress applications.
Mechanical Properties of 7075-T76 Aluminum
| Property | Value |
| Tensile Strength | Approximately 560 MPa |
| Yield Strength | Around 480 MPa |
| Elongation at Break | Roughly 7.9% |
| Fatigue Strength | 190 MPa (improved over T6) |
| Hardness (Brinell) | Range of 150 |
Thermal and Electrical Properties of 7075-T76 Aluminum
| Property | Value |
| Thermal Conductivity | Approximately 130 W/m-K |
| Specific Heat Capacity | Around 870 J/kg-K |
| Thermal Expansion | About 23 µm/m-K |
| Melting Range | 480°C (solidus) to 640°C (liquidus) |
| Electrical Conductivity | Approximately 33% IACS by volume (or 98% on weight basis) |
Processing and T76 Condition
Heat Treatment:
The alloy is first solution heat treated and quenched (such as the T6 process), followed by an over-aging step to achieve the T76 condition.
Advantages of T76 Condition
- Improved fatigue strength: The T76 condition provides enhanced fatigue resistance, which is crucial for components subjected to cyclic loads.
- Enhanced stress corrosion resistance: Over-aging minimizes internal stresses, preventing cracking under stress and corrosive environments.
Machinability and Weldability:
While 7075 alloy is generally well-suited for machining, it is not suitable for welding due to its susceptibility to cracking, and the T76 condition retains this characteristic.
7075 T76 Aluminum Corrosion Resistance and Durability
- Compared to T6, the T76 condition significantly improves resistance to exfoliation corrosion, making it an ideal choice for marine and aerospace environments.
- The stability of the microstructure enhances stress corrosion cracking resistance.
7075 T76 Aluminum Applications
Due to its excellent mechanical properties and durability, 7075-T76 aluminum is widely used in:
| Application Field | Description |
| Aerospace | 7075-T76 aluminum is widely used in aerospace due to its excellent strength, corrosion resistance, and fatigue resistance. It is commonly used in the manufacturing of aircraft structural components, such as fuselage frames, support components, and precision parts. The high strength and excellent fatigue performance of 7075-T76 aluminum allow it to withstand extreme pressures and cyclic loads during flight, ensuring the long-term safety and reliability of aircraft. |
| Defense | 7075-T76 aluminum is the material of choice for many military devices and components, especially in applications requiring high strength and fatigue resistance. It performs excellently in the military field, used in the production of lightweight weapons (such as the receivers of rifles and other critical components) and other parts that must endure repeated cyclic stress. Its high strength-to-weight ratio allows it to reduce the overall weight of equipment while maintaining high strength, making it an indispensable material in modern military equipment. |
| Automotive and Sports Equipment | The high strength and lightweight properties of 7075-T76 aluminum make it widely used in high-performance automobiles and sports equipment. Racing car frames, bicycle components, sports equipment, and other parts require this material to ensure strength and durability in extreme sports. 7075-T76 aluminum provides excellent strength-to-weight ratio, allowing sports equipment to maintain superior performance while being robust. |
| Specialized Machinery | 7075-T76 aluminum is often used in the manufacture of precision tools and components for industrial applications that need to withstand high stress. Its high strength and good machinability make it suitable for the production of precision tools and equipment components, which often face extreme working environments and high loads. The stability and durability of 7075-T76 aluminum ensure that these mechanical parts remain efficient in high-pressure work for extended periods. |
| Industrial | In the industrial field, 7075-T76 aluminum is used in mold manufacturing, precision rifles (such as M16 receivers), and rock climbing equipment. Due to its extremely high strength and corrosion resistance, 7075-T76 aluminum is widely used in these industrial products requiring high strength and durability. Whether in military applications or extreme sports equipment, the reliability and durability of 7075-T76 aluminum make it the material of choice. |
| Sheet Products | 7075-T76 aluminum can also be used to manufacture bare sheets or Alclad sheets to enhance its corrosion resistance. Alclad sheets are composed of 7075 aluminum with a thin layer of aluminum alloy on the surface, which significantly improves the sheet's corrosion resistance, making it especially suitable for aerospace, marine, or other industrial applications where high corrosion resistance is required. |
7075 T76 Aluminum Compared to Other Conditions
| Comparison Item | Description |
| Compared to T6 | 7075 T76 aluminum is comparable to T6 aluminum in terms of tensile and yield strength, but T76 aluminum alloy offers superior fatigue and corrosion resistance. While T6 state 7075 aluminum exhibits excellent strength, T76 aluminum, due to improvements from the over-aging process, shows higher corrosion resistance and better fatigue strength, making it more suitable for applications that endure repeated loads and harsh environmental conditions. |
| Compared to T73 | 7075 T76 aluminum and T73 aluminum are similar in corrosion resistance, but T76 aluminum has higher strength. T73 state 7075 aluminum is typically used in applications with high corrosion resistance requirements, while T76 state offers a more significant advantage in strength, making it suitable for structural components requiring higher load-bearing capacity. Although both states offer similar corrosion resistance, T76 stands out in high strength and durability. |
7075 T76 Aluminum Standards and Availability
- Certified to ASTM B209 and AMS-QQ-A-250/24.
- Available in sheet, plate, rod, and extrusions, with thicknesses ranging from 0.016 to 0.190 inches.
7075 T76 Aluminum Limitations
- Weldability: Poor weldability; resistance welding is preferred.
- Formability: Limited at room temperature, but can be improved with high-temperature techniques (e.g., warm forming).
7075 T76 strikes a balance between strength and environmental durability, making it a preferred choice for industries prioritizing service life under pressure. Its over-aged microstructure ensures reliability in corrosive environments while maintaining strength levels close to that of T6. For applications requiring performance and corrosion resistance, T76 provides a versatile and robust solution.
7075-T76 aluminum stands out for its high strength, excellent fatigue performance, and superior stress corrosion cracking resistance, all achieved through the over-aging process following the standard T6 treatment. These characteristics make it an ideal choice for harsh environments such as aerospace, defense, and high-performance engineering applications.
