EN AW-7075 Aluminium Alloy: Properties, Applications, and Equivalents
EN AW-7075 is a high-strength aluminium alloy that offers excellent performance in demanding environments. Known for its exceptional strength-to-weight ratio, this alloy is widely used in aerospace, motorsport, and precision tooling where mechanical strength is critical but weight reduction is equally important. In this article, we explore the chemical composition, mechanical properties, applications, and international equivalents of EN AW-7075, along with key comparisons to other common aluminium grades.
What is EN AW-7075?
EN AW-7075 is a wrought aluminium alloy primarily alloyed with zinc, magnesium, and copper. It belongs to the 7000 series of aluminium alloys, which are known for their high strength and heat treatability. Often designated as AlZn5.5MgCu, EN AW-7075 is particularly valued in aerospace-grade applications due to its high tensile strength and fatigue resistance.
Chemical Composition of EN AW-7075
EN AW-7075 is predominantly an aluminium alloy with zinc (5.1-6.1%) as its primary alloying element, providing significant strength through solid solution strengthening and precipitation hardening. Magnesium (2.1-2.9%) and copper (1.2-2.0%) are also critical additions, with magnesium forming strengthening precipitates like MgZn₂ and copper further enhancing ultimate tensile strength. Minor additions like chromium contribute to improved stress corrosion cracking resistance.
| Element | Percentage(%) |
|---|---|
| Aluminium (Al) | Balance |
| Zinc (Zn) | 5.1 – 6.1 |
| Magnesium (Mg) | 2.1 – 2.9 |
| Copper(Cu) | 1.2 – 2.0 |
| Other (Fe, Si, Mn, Cr, Ti) | Trace |
Physical Properties of EN AW-7075
| Property | Value |
|---|---|
| Density | Approx. 2.81 g/cm³ (0.102 lb/in³); slightly higher than pure aluminium due to alloying elements |
| Melting Range | 477–635 °C (890–1175 °F); range due to alloy composition |
| Thermal Conductivity | Typically ~130 W/m·K |
| Electrical Conductivity | Approx. 33% IACS (International Annealed Copper Standard) |
| Coefficient of Thermal Expansion (CTE) | Approx. 23.6 µm/m·°C (20–100 °C); important for thermal stability |
| Elastic Modulus (Young’s Modulus) | Approx. 70–72 GPa |
| Shear Modulus | Approx. 26–27 GPa |
| Poisson’s Ratio | Approx. 0.32–0.33 |
Mechanical Properties of EN AW-7075
The mechanical performance of EN AW-7075 varies depending on the temper. Below are typical values for T6 and T73 conditions:
| Property | T6 Temper | T73 Temper |
|---|---|---|
| Tensile Strength (MPa) | 540 – 570 | 480 – 510 |
| Yield Strength (MPa) | 470 – 500 | 400 – 440 |
| Elongation (%) | 5 – 11 | 9 – 13 |
| Brinell Hardness (HB) | 150 – 160 | 130 – 140 |
Key Features and Benefits of EN AW-7075
- Outstanding strength-to-weight ratio
- Excellent fatigue resistance
- Good machinability
- Moderate corrosion resistance (can be enhanced with surface treatments)
- Limited weldability – mechanical fastening is preferred
- Available in a variety of tempers
- Corrosion resistance
Fabrication and Processing of EN AW-7075
EN AW-7075’s high strength significantly impacts its fabrication, making specific processing considerations essential.
Machinability:
Excellent machinability in the T6/T651 temper makes 7075 highly suitable for precision CNC operations. Its hardness allows for fine chip formation and good surface finishes, though robust tooling is needed.
Formability:
Limited formability at room temperature in high-strength tempers (T6/T651) means severe bending is difficult. For complex shapes, forming in the annealed (O) temper or utilizing warm/hot forming methods is recommended, followed by heat treatment for final properties.
Weldability:
EN AW-7075 has poor weldability due to susceptibility to hot cracking and significant strength loss in the heat-affected zone. Fusion welding (TIG/MIG) is generally avoided for critical structural uses. Resistance welding is often the preferred joining method, minimizing HAZ effects.
Forging:
Excellent for forging, 7075 produces high-strength, durable components with refined grain structures, improving fatigue and fracture toughness. Typical forging temperatures are 370-430 °C (700-800 °F).
Surface Treatment:
o Anodising: Readily anodized for improved corrosion and wear resistance. Note that high zinc content can result in a brownish tint in the coating.
o Painting/Coating: Standard practice for enhanced corrosion protection, particularly in external environments.
Common Applications of EN AW-7075
Due to its strength and light weight, EN AW-7075 is used in:
EN AW-7075 vs Other Aluminium Grades
When comparing EN AW-7075 to other aluminium alloys, several key performance characteristics stand out. EN AW-7075 is best known for its exceptionally high strength-to-weight ratio, making it a popular choice in aerospace and high-performance engineering applications. In contrast, EN AW-6061 (equivalent) offers moderate strength but far superior weldability and corrosion resistance, which makes it a more versatile and economical option for structural and marine use. While it cannot match 7075 in mechanical strength, its ease of machining and joining make it suitable for a broader range of fabrication processes.
EN AW-5052 (equivalent)
EN AW-5052 is a non-heat-treatable aluminium alloy with excellent corrosion resistance, especially in saltwater environments. It has lower strength compared to both 7075 and 6061, but it compensates with outstanding formability and weldability, which is why it is commonly used in marine components, fuel tanks, and enclosures. Its relatively low cost also makes it ideal for high-volume manufacturing where extreme mechanical performance is not required.
EN AW-2017 (equivalent)
On the other hand, EN AW-2017 offers high strength and is often used in aerospace and automotive industries. However, its corrosion resistance is notably lower, and it has limited weldability, requiring protective coatings or treatments in harsher environments. While similar in strength to 7075, 2017 is heavier and generally considered less fatigue-resistant, though still useful in components where mechanical performance is critical and cost is a concern.
In summary, the choice between these aluminium alloys depends on the specific needs of the application. EN AW-7075 is the top performer in terms of strength and fatigue resistance but comes with trade-offs in machinability, weldability, and price. Meanwhile, 6061 and 5052 offer better corrosion resistance and ease of processing, and EN AW-2017 serves as a high-strength alternative where corrosion is less of a factor.
| Grade | Strength | Corrosion Resistance | Weldability | Cost | Typical Applications |
|---|---|---|---|---|---|
| EN AW-7075 | Very High | Moderate | Poor | High | Aerospace, tooling, motorsports |
| EN AW-6061 equiv. | Medium | Good | Good | Moderate | Structural, marine, general-purpose |
| EN AW-5052 equiv. | Low–Medium | Excellent | Excellent | Low | Tanks, marine, enclosures |
| EN AW-2017 equiv. | High | Low–Moderate | Poor | High | Rivets, aerospace fasteners |
Machinability and Processing Considerations
EN AW-7075 offers good machinability in the T6 condition. It produces short chips and responds well to precision cutting, drilling, and tapping. However:
- Weldability is generally poor – mechanical fasteners or adhesives are preferred.
- Corrosion resistance can be improved with anodising or cladding.
- The alloy is highly responsive to heat treatment – temper selection affects strength and ductility.
EN AW-7075 Availability and Forms
EN AW-7075 is commercially available in various formats:
- Rolled plates and sheets
- Round and flat bars
- Extruded profiles
- Forged blanks
- Precision CNC milled parts (available through platforms like meviy)
Conclusion
EN AW-7075 is one of the strongest aluminium alloys available and remains a top choice in aerospace, motorsport, and precision engineering where high strength and reduced weight are essential. While it comes at a premium and has limited weldability, its performance in demanding applications is unmatched.
EN AW-7075 is a premier high-strength aluminium alloy, primarily alloyed with zinc, magnesium, and copper, known for its exceptional strength-to-weight ratio in the T6 temper. While it boasts good machinability and forgeability, its weldability is poor due to hot cracking susceptibility, typically requiring specialized resistance welding. This alloy is widely utilized in demanding aerospace and defense applications where structural integrity and lightweight design are critical, often benefiting from anodizing or coatings for enhanced corrosion resistance, although specific tempers like T73 are developed to mitigate its vulnerability to stress corrosion cracking.
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