What are the Main Differences between Aluminum 6061 and 7075
Aluminum is available in many different alloys, but 6061 and 7075 are two of the most commonly used grades for CNC machining. The two offer different levels of strength, machinability, corrosion resistance, and cost. This article compares their key properties to help you choose the right alloy for your application.
What is 6061 aluminum alloy?
6061 aluminum alloy is a 6000 series heat-treatable, strengthened aluminum alloy mainly composed of aluminum, magnesium, and silicon. It is often used for CNC turning and milling parts.
What is 7075 aluminum alloy?
7075 is a heat-treatable 7000-series aluminum alloy that uses zinc as its primary alloying element, with magnesium and copper also contributing to its high strength.
Main differences between Aluminum 6061vs7075
7075 aluminum vs 6061 are both common materials for CNC machining. However, they differ significantly in terms of alloy elements, strength, and machinability. When designing aluminum parts, you need to comprehensively consider whether the different properties between them meet your actual requirements.
Alloy composition
Both 6061 and 7075 are aluminum alloys, but there are significant differences in the content of other alloying elements in them. See the differences between 6061 aluminum VS 7075 aluminum as follows:
| Main Elements | 6061 Aluminum | 7075 Aluminum |
| Mg | 0.8–1.2% | 2.1–2.9% |
| Si | 0.4–0.8% | ≤0.4% |
| Cu | 0.15–0.4% | 1.2–2.0% |
| Zn | ≤0.25% | 5.1–6.1% |
| Cr | 0.04–0.35% | 0.18–0.28% |
| Mn | ≤0.15% | ≤0.3% |
| Ti | ≤0.15% | ≤0.20% |
| Fe | ≤0.70% | ≤0.5% |
Strength and hardness
Both 6061 and 7075 are heat-treatable alloys, but 7075-T6 is significantly stronger and harder than 6061-T6. 7075-T6 offers significantly higher strength, while 6061-T6 is generally easier to machine and more cost-effective.
| Mechanical Properties | 6061-T6 | 7075-T6 |
| Tensile Strength | ≈ 310 MPa | ≈ 572 MPa |
| Yield Strength | ≈ 276 MPa | ≈ 503 MPa |
| Brinell Hardness | ≈ 95 HB | ≈ 150 HB |
The data above show a substantial strength advantage for 7075-T6. With the same material volume and similar part geometry, a 7075-T6 component can withstand higher loads and better resist permanent deformation than a 6061-T6 component.
Density and weight
At room temperature, aluminum 6061 density is approximately 2.70 g/cm³, and 7075 aluminum density is approximately 2.81 g/cm³. The density of 7075 is slightly higher than that of 6061. This means that in the same volume, the weight of the 7075 parts you designed is approximately 4% higher than that of 6061.
Although the density of 7075 is slightly higher, it has significantly higher strength. Therefore, if the CNC aluminum parts you design require high strength, you can reduce the size or thickness of some structural parts to lower the weight of the parts.
Elastic modulus and rigidity
Elastic modulus measures a material’s resistance to elastic deformation. A higher modulus means less deformation under identical load and section conditions. The elastic modulus of 6061 aluminum alloy is usually about 68.9 GPa, and that of 7075 is about 71.7 GPa. Therefore, in terms of rigidity, there is no significant difference between the two.
If you consider whether the parts are prone to deformation during the design process, in addition to considering the elastic modulus of the material itself, you also need to consider the structural size and geometric shape of the aluminum parts.
CNC machining performance
6061 is relatively easy to achieve stable processing results in common processing processes such as CNC milling, turning, drilling, and tapping. For the parts with a relatively complex structure you designed, 6061 usually has better processing adaptability. At the same time, 6061 has a relatively smaller burden on the cutting tool during processing, and the tool wear is usually easier to control.
7075 has significantly higher mechanical strength and hardness than 6061. Therefore, when choosing tools, cutting speeds, etc., according to the requirements of your drawings, you need to make reasonable selections. Unreasonable choices may increase tool wear and affect processing efficiency and the surface quality of the parts. However, 7075 still belongs to aluminum alloys with good CNC machining performance and is not a difficult-to-process material.
Corrosion resistance
6061 contains main alloy elements such as magnesium and silicon, and can form a relatively stable oxide film on the surface, providing your parts with certain natural protection. Therefore, 6061 has good corrosion resistance in humid environments, general outdoor environments, and common industrial environments.
The main alloy elements of 7075 include zinc, magnesium, and copper. The copper content is relatively high, and it is more sensitive to corrosion in humid, salt fog, and certain corrosive environments. Especially when specific stress and corrosive media exist simultaneously, 7075 also needs to pay attention to the risk of corrosion cracking.
Surface treatment
6061 can undergo Type II and Type III anodizing, and it can also be anodized according to the Pantone color chart. The anodizing performance is usually more stable, and it is easier to obtain relatively uniform colors and surface effects.
7075 can also be anodized, but the final colored anodizing effect of the designed part will be affected by multiple factors such as material batch and alloy content. Stricter control is required for the surface treatment process of 7075.
How to choose the right materials for your parts?
When choosing the raw materials, you should not only consider the material’s properties, but also take into account the actual usage conditions of your parts and the budget cost, etc., to select a more suitable material.
Mechanical performance requirements
The densities and elastic moduli of 6061 and 7075 are relatively close, but 7075 has significantly higher strength. Therefore, if your design focus is on improving the bearing capacity and you also want to maintain a high strength-to-weight ratio, 7075 has an advantage; if the strength requirement is not high, you can also consider 6061.
Working environment of the parts
During the design process, you need to consider whether the parts will come into contact with water, salt spray, or other corrosive media during actual use. If the usage environment is harsh, 6061 is more recommended than 7075.
Cost
During the design process, you should not only consider the cost of the raw materials, but also take into account the cost of CNC machining and the cost of surface treatment. If 6061 meets your requirements, there is no need to choose the more expensive 7075.
Common applications of 6061 vs 7075 aluminum
The performance differences between 6061 and 7075 also determine that they are used in different actual application areas in the parts you design. Below are the main applications of these two materials.
6061
- Mechanical parts: brackets, connecting pieces, sleeve parts, fixtures, etc. CNC-processed components
- Structural parts: enclosures, support pieces, guide rail components, etc.
- Automobile parts: automotive structural parts, chassis parts, hub-related parts
- Electronic equipment parts: equipment enclosures, installation components, etc.
7075
- Aerospace parts: aircraft structural components, aviation connectors, etc.
- High-strength mechanical parts: gears, shaft parts, etc.
- Automobile parts: suspension-related parts, etc.
- Sports equipment: bicycle parts, mountaineering equipment, etc.
- High-performance equipment parts: CNC-processed parts with high requirements for strength-to-weight ratio
FAQ
Q: Why is 7075 not weldable?
A: 7075 aluminum features poor weldability. Its high zinc, magnesium, and copper content easily causes hot cracking during welding. Meanwhile, welded joints suffer severe strength loss and residual stress, so welding is generally not recommended for 7075 structural components.
Q: How to tell if aluminum is 6061 or 7075?
A: It is difficult to distinguish whether it is 6061 or 7075 from its appearance. It needs to be confirmed through material identification or by using material testing methods such as spectroscopic analysis.
Q: Is 7075 aluminum better than 6061?
A: No. Although 7075 has higher strength, 6061 has advantages over 7075 in terms of machinability, corrosion resistance, and cost.
Q: Is 7075 more expensive than 6061?
A: Yes. 7075 aluminum is generally more expensive than 6061, mainly due to its different alloy composition and higher production costs.
Q: Can 6061 and 7075 aluminum be used together?
A: Yes. However, it needs to be evaluated based on the specific connection method, working environment, and corrosion risk.
Q: How much heavier is 7075 than 6061?
A: Under the same volume, 7075 is approximately 4% heavier than 6061.
Final Thoughts
Shanghai Yecheng provides CNC machining for 6061 and 7075 aluminum components. We have our own in-house sandblasting machines and anodizing facilities, which can fully meet your one-stop machining needs. If you are currently looking for a reliable and long-term factory partner, please feel free to contact us.
