In this guide, you will learn about 7075 aluminum: its composition, unique features, advantages, disadvantages, and applications. Let’s take a closer look at its main features and the fields where this high-performance alloy is employed.
What is 7075 Aluminium?
7075 aluminum is a commercial alloy. It comprises aluminum, zinc, magnesium, and copper content. Typically, it belongs to the 7xxx group of the aluminum family. These alloys are widely applicable in high-strength applications due to their strength/weight ratio, which allows them to have a variety of uses for aerospace, military, and other applications needing substantial strength.
In addition, 7075 aluminum has a high zinc content (5.6-6.1% by weight) and as a result, offers a high strength-to-weight ratio. However, it is less formable more challenging to weld, and resistive to corrosion. Therefore, it may need to be anodized or coated for exploitation in harsh environments.
Key Elements in 7075 Aluminium Composition
- Aluminum (Al): 87.1% – 91.4%
- Zinc (Zn): 5.6% – 6.1%
- Magnesium (Mg): 2.1% – 2.9%
- Copper (Cu): 1.2%
- Chromium (Cr): 0.18% – 0.28%
- Manganese (Mn): 0.3%
- Silicon (Si): 0.4%
- Iron (Fe): 0.5% max
How Tempering Affects Aluminium Alloy 7075 Mechanical Properties
Tempering has an explicit effect on the mechanical properties of 7075 aluminum. Normally, it impacts its strength, hardness, and ductility. In alloy tempering, it is heated to a certain temperature. Then, quenched to solidify the microstructure, and aged to improve its properties.
Strength: Strengthening 7075 aluminum makes it rigid. Usually, it is done by forming a substance called MgZn₂, which increases the material’s hardness. This leads to an improved tensile strength and makes it useful for manufacturing aircraft components, and weapons.
Hardness: Tempering alters the alloy using deterioration during the aging process. Thus, increasing the hard surface of the alloy to resist wearing and deformation. However, over-tempering can slightly reduce its hardness.
Ductility: Whereas the process of tempering intensifies the strength and hardness of aluminum, it also lowers its ductility. Different temper designs such as T6 offer more strength at the reduced elongation which makes the alloy more rigid and susceptible to brittle failure when under stress.
Stress Resistance: Alloy 7075 in the tempered condition provides better stress corrosion cracking and fatigue properties than the standard 7075 aluminum when used under heavy structural applications.
Where 7075 Aluminum Alloy Is Used?
7075 aluminum alloy is usually employed in areas that require strong and light metals in operations. So, the aerospace industry is a primary consumer of aluminum 7075 and 7075 aluminum extrusions for crafting aircraft structures, fuselage frames and wings, and wing spars.
Furthermore, it is used in military applications like weapons and marine applications like structures where the material has to be high-stress resistive. In addition, it is also used in vehicle applications, including racing cars, and in sporting equipment, including bikes and clubs.
Physical Properties of 7075 Aluminium
- Density: 2.81 g/cm³
- Melting Point: 475–635°C (880–1,175°F)
- Thermal Conductivity: 130 W/m·K
- Electrical Conductivity: 30% IACS
- Modulus of Elasticity: 71.7 GPa
- Coefficient of Thermal Expansion(k): 23.6 µm/m·K
- Specific Heat: 0.96 J/g·K
- Tensile Strength: Up to 572 MPa (T6 temper)
Advantages of 7075 Aluminium
- Good Machinability
- Good Fatigue Resistance (can handle repeated stress without failing)
- Moderately Heat Treatable
- Moderate Formability (can be shaped, but not as easily as some other alloys)
- Weldable (can be welded, though strength may decrease in welded areas)
Limitations of Aluminium 7075
- Poor Weldability (welding may lead to alloy degradation)
- Low Formability (slightly more rigid than most other aluminum alloys)
- Cost:(7075 aluminum alloy is relatively costlier).
- Susceptible to Stress Corrosion (material is vulnerable to stress corrosion cracking in some conditions)
- Difficult to Fabricate:(categorized under hard materials because it needs special equipment and specific processing techniques to work on).
Aluminium 6061 vs 7075 – Technical Comparison
| Property | Aluminium 6061 | Aluminium 7075 |
| Tensile Strength | 240–310 MPa | 510–572 MPa |
| Yield Strength | 205 MPa | 450 MPa |
| Density | 2.70 g/cm³ | 2.81 g/cm³ |
| Corrosion Resistance | Excellent | Moderate |
| Machinability | Excellent, easy-to-machine | Good, but harder due to higher strength |
| Formability | Excellent, good for extrusion/rolling | Poorer, more prone to cracking during forming |
| Weldability | Very good, especially in the T6 temper | Poor, can weaken in welded areas |
| Heat Treatment | T6, T651 temper for strength | T6 temper for maximum strength |
| Fatigue Resistance | Good, suitable for moderate stress | Excellent, handles high-stress conditions |
| Applications | Structural, automotive, aerospace | Aerospace, military, high-stress applications |
| Cost | Lower cost | Higher cost due to high strength |
Forms/Variants of 7075 Aluminium Alloy
- 7075-O (Annealed)
- 7075-T6 (Solution heat-treated and artificially aged)
- 7075-T651 (T6 temper with stress relief)
- 7075-T73 (Solution heat-treated and stabilized)
- 7075-T7351 (T73 temper with stress relief and stabilized)
- 7075-T7 (Overaged, maximum strength)
- 7075-T76 (Solution heat-treated, stabilized, and stress-relieved)
Main Finishes for 7075 Aluminium Alloy
The common finishes for aluminum 7075 include:
Anodized Finish
Anodizing refers to an electrolytic procedure that signifies the natural oxide layer of aerospace grade 7075 aluminum. Moreover, it improves its corrosive, abrasive, and surface hardness properties. Additionally, It increases the alloy’s ability to resist corrosion in hostile conditions and can be colored to suit specific uses. Thus, these coatings are mainly used in aerospace, military, and high-performance engineering.
Mill Finish
The mill finish of 7075 aluminum is the natural finish surface after passing through the rolling, and extrusion techniques. It has a sort of matte metallic sheen and may entail small pitting on the surface.
Powder Coating
Powder coating uses an electrostatically charged powder; applied to 7075 aluminum and then heat solidified. Such coating gives excellent defense against corrosion, wear, and mechanical shock and normally comes in many colors and finishes. Typically it is applied to architectural, automotive, and outdoor areas where product appearance, and longevity matter.
Difference Between 2024 and 7075 Aluminium
2024 aluminum is less prone to fatigue, and invaluable for the long-term performance of aircraft structures. On the other hand, 7075 aluminum offers higher mechanical strength in a general sense. It is used when maximum strength is needed but it is more prone to corrosion and less fatigue resistant than 2024.
Conclusion
7075 aluminum has excellent tensile strength and offers high durability. So, its use is common for superfluous applications such as aerospace and military. Though it has a superior strength-to-weight ratio and fatigue properties, it lacks corrosion resistance and is complex to machine. Therefore, it’s crucial to choose the right temper and finish.
