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6061 vs 7075 Aluminum: Which One to Choose?

6061 vs 7075 Aluminum - https://jiahuicustom.com/

Aluminum alloys are the backbone of various manufacturing industries nowadays. Whenever it comes to choosing a material featuring excellent strength, corrosion resistance, machinability, hardness, and conductivity, aluminum is the top priority of maximum engineers.

However, aluminum alloys are further distributed into several grades based on their chemical composition. Two significant examples include 6061 and 7075 aluminum. These aluminum alloys are somewhat different from each other.

In most cases, it gets difficult to choose between both aluminum alloys. This article will help you differentiate between these aluminum alloys to select one suitable for your application.

 

What is the Alloy Series?

As you know, an alloy combines two or more chemical elements, of which at least one is a metal. However, the alloys which belong to a similar series are called alloy series. They show various identical properties, including corrosion resistance, mechanical properties, extrudability, castability, etc.

Aluminium alloys contain aluminum as a predominant element, yet different alloying elements such as magnesium, copper, silicon, zinc, nickel, and manganese can be used in different series. For instance, 3xxx-series alloys are significantly alloyed with manganese, 5xxx-series alloys are alloyed with magnesium, and the highest strengthened 7xxx-series alloys are alloyed with zinc.

 

What is 6061 Aluminum Alloy?

One of the outperforming members of the 6000 alloy series is the 6061 aluminium alloy. The primary alloying elements of this series are magnesium (0.8%~1.2%) and silicon (0.4%~0.8%). 6061 aluminum is primarily used in forming automotive, aerospace, electrical, piping, and consumer products.

Typically, this alloy is known for its excellent tensile strength, which is increased by the heat treatment process. Some other remarkable properties of 6061 aluminum alloy include good machinability, workability, weldability, and corrosion resistance. As it is easy to deal with, you can prefer it for extrusion projects.

Moreover, its density is almost the same as pure aluminum metal or 2.7g/cm3.

 

What is 7075 Aluminum Alloy?

7075 aluminum is another highly strengthened alloy belonging to the 7000 series. The central alloying element of this aluminum alloy is zinc (5.1%~6.1%). This alloy is considered the strongest type of aluminum, yet it reduces the workability and weldability of the part. Usually, defense and aerospace industries prefer to use 7075 aluminum. In terms of density, this alloy exhibits higher density than pure aluminum, about 2.8 g/cm3.

In comparison to 6061 aluminum, it’s more expensive. Additionally, the higher concentration of copper affects the corrosion resistivity of 7075 aluminum. Thus, it is more likely to be affected by caustic environments.

 

6061 vs 7075 Aluminum: The Differences and Characteristics

6061 and 7075 aluminum show similarities as well as some different characteristics. The following are some properties that are different for both aluminum alloys:

6061 vs 7075:  Chemical Composition

The first point of difference is the chemical composition of alloying elements in each aluminum alloy. The below table talks about the percentage composition of different elements;

Chemical Elements 6061 Al Composition 7075 Al Composition
Zinc 0.25% 5.1%~6.1%
Silicon 0.4%~0.8% <0.4%
Magnesium 0.8%~1.2% 2.1%~2.9%
Copper 0.15%~0.4% 1.2%~2.0%
Chromium 0.04%~0.35% 0.18%~0.28%
Zirconium 0.03%
Titanium 0.20% 0.15%

Cost

When it comes to cost, 7075 aluminum alloy is an expensive option as it’s the strongest and lightest aluminum. On the other hand, 6061 is also a suitable aluminum alloy and is more economical than 7075 aluminum. The average cost of 6061 alloys is  2.6 to 4.3 USD per kilogram and 6 to 8.6 USD per kilogram for 7075 alloys.

 

Comparison of 6061 vs 7075 Aluminum Based on Properties

1. 6061 vs 7075 Aluminum: Mechanical Properties

  • Yield Strength

6061 aluminum alloy is characterized by a relatively moderate yield strength. In the 6061-T651 aluminum temper, the typical yield strength is around 276 MPa. 7075 aluminum alloy is renowned for its exceptionally high yield strength, making it one of the strongest aluminum alloys. In the T6 temper, 7075 typically exhibits a yield strength of aluminum approximately 480 MPa or even higher.

  • Material Hardness

6061 aluminum alloy is renowned for its excellent balance of strength and workability. Aluminum 6061-T6 hardness ranges from 95-97 Brinell hardness (HB), one of the most commonly used tempers for 6061. This hardness level is moderate and allows for machining, forming, and welding relatively quickly.

7075 aluminum alloy, in contrast, is known for its remarkable strength, making it one of the strongest aluminum alloys available. It typically boasts a higher material hardness than 6061, often ranging from 150 to 160 Brinell hardness (HB) when in the T651 temper. The T6 temper for 7075 involves a similar heat treatment process as 6061 but results in a significantly harder material.

2. 6061 vs 7075 Aluminum: Physical Properties

  • Electrical Resistivity

Electrical resistivity is a measure of how well a material can conduct electricity. In the world of aluminum alloys, it helps determine their suitability for electrical uses. Among these alloys, 6061 is a top pick due to its strong ability to let electricity flow through it.

This alloy’s electrical resistivity is lower than 7075, showcasing its superior performance as an electrical conductor. The reason behind this discrepancy lies in the alloy’s elemental composition. 6061 primarily consists of aluminum, magnesium, and silicon, contributing to its excellent electrical properties.

In contrast, 7075 aluminum alloy exhibits a slightly higher electrical resistivity than 6061. This can be attributed to its different composition, which includes higher levels of zinc and copper. While these elements enhance 7075’s mechanical properties, they can also introduce a slightly higher resistance to the flow of electrical current.

  • Elasticity

6061 aluminum alloy exhibits good elasticity, making it a relatively malleable material. It can deform under stress, such as bending or stretching, and recover its original shape when released. 7075 aluminum alloy, while exceptionally strong and stiff, is generally less elastic than 6061. This means it is less ductile and less likely to deform significantly under the yield stress of aluminum while maintaining its original shape.

  • Density

Density is a fundamental property that measures the mass of a material per unit volume. The density of 6061 aluminum is relatively low, typically averaging around 2.70 g/cm³ (0.0975 lb/in³). This low density contributes to its lightweight nature, making it a preferred choice for applications where weight savings are crucial, such as in the aerospace and automotive industries.

7075 aluminum alloy is denser than 6061. It has a higher density, usually around 2.81 g/cm³ (0.1015 lb/in³). While still considered lightweight compared to many other materials, its greater density results from its specific composition and higher content of heavy alloying elements.

3. 6061 vs 7075 Aluminum: Chemical Properties

  • Corrosion Resistance

6061 aluminum alloy is known for its relatively good corrosion resistance. This is primarily due to its composition, which contains lower levels of copper than 7075. Copper is inherently more reactive when exposed to caustic or corrosive environments, making alloys with higher copper content more susceptible to corrosion.

The low copper content in 6061 helps it withstand a broader range of environmental conditions without significant degradation. On the other hand, 7075 aluminum alloy, with its higher copper content, is more vulnerable to corrosion. While it offers excellent mechanical properties, particularly in high-stress applications, its corrosion resistance is lower than 6061.

  • Thermal Conductivity of Aluminum

Thermal conductivity is another of the most critical factors when comparing 6061 and 7075 aluminum alloys. While both alloys exhibit good heat conduction properties, 6061’s slightly higher thermal aluminum conductivity makes it an excellent choice for applications where efficient heat dissipation is paramount, such as heat exchangers and thermal management systems.

  • Temperature Hardness

When comparing the temperature hardness of 6061 and 7075 aluminum alloys, it’s evident that 6061 maintains better hardness up to approximately 533°C (990°F), making it a more suitable choice for applications where high-temperature hardness retention is necessary. In contrast, 7075 experiences a more pronounced reduction in hardness, particularly above 100°C (212°F), which may limit its effectiveness in elevated temperature environments where hardness is a critical consideration.

4. 6061 vs 7075 Aluminum: Processing Properties 

  • Welding

When comparing the welding properties of 6061 and 7075 aluminum alloys, we find that 6061 is known for its favorable welding characteristics thanks to its higher elasticity, which makes it convenient to weld and form using common welding methods. This, coupled with its balanced mechanical properties and good corrosion resistance, positions 6061 as an excellent choice for welding applications.

However, 7075 aluminum alloy is regarded as less weldable, primarily due to its lower ductility and heightened strength, making welding of 7075 aluminum more challenging. Its susceptibility to heat cracking during the welding process leads to the recommendation of alternative joining methods, with fasteners like rivets being a preferred choice.

  • Machinability and Fabrication Considerations

Machinability and fabrication of the material are crucial factors in manufacturing products with great ease. As 6061 aluminum is not as hard as 7075 aluminum, it’s pretty easy to machine this alloy. The popular machining processes include cutting, die-casting, and milling. In short, 6061 aluminum has better formability.

Characteristics 6061 Aluminum 7075 Aluminum
Yield Strength Moderate, approx. 276 MPa Exceptionally high, approx. 503 MPa
Material hardness Moderate, 95-97 Brinell hardness (HB) High, 150-160 Brinell hardness (HB
Electrical resistivity Lower resistivity Slightly higher resistivity
Elasticity Relatively malleable and ductile Stiffer and less elastic
Density Low density (2.70 g/cm³ High density (2.81 g/cm³)
Corrosion Resistance Good corrosion resistance Vulnerable to corrosion
Thermal conductivity Good thermal conductivity Slightly lower thermal conductivity
Temperature 533°C (990°F) 100°C (212°F)
Welding Favorable welding Less weldable
Machinability Good Relatively lower

 

6061 vs 7075 Aluminum: Applications

Applications of 6061 Aluminum

The remarkable properties of 6061 aluminum allow it to be used in various applications. The following are typical applications:

  • The automotive industry prefers it for fuel efficiency and cost-effectivity.
  • The aircraft industry uses it for good weldability to join different aircraft parts.
  • It is suitable for the marine industry due to its high corrosion resistance. In some cases, additional coatings or finishes might be needed to provide the best corrosion resistance. Usually, finishing equipment, docks, mooring, marine firearms, and scuba diving equipment.
  • The building construction industry also uses 6061 aluminum—for instance, stairs, cover plates, flooring, subway platforms, etc.
  • The good electrical conductance of 6061 aluminum makes it perfect for manufacturing electronics.
  • Some other applications are consumer products such as bicycle frames, piping, etc.

Applications of 7075 Aluminum

The following are significant applications of 7075 aluminum:

  • It is popular in the aviation industry for its high strength and weight.
  • Used to produce the equipment required for rock climbing and inline skating.
  • 7077 aluminum is the best material for industrial tooling, molding, firearms, and camping utensils.
  • The transportation industry also uses it for the production of various complex components.
  • Some other applications include gears, shafts, regulating valves, missile components, fuse parts, etc.

 

How to Choose Between 6061 and 7075 Aluminum Alloy?

Until now, you have gained enough knowledge about the characteristics of both aluminum alloys. The next step is to decide on one for your application, which is tricky. The following conditions for which 6061 aluminum is a perfect option:

  • If you need to weld the part often and it needs a lot of machining, you must go for it.
  • Aluminum 6061 should be your choice if you want a corrosion-resistant product.
  • It can be an excellent material if cost is your issue, as it’s cheaper than 7075 aluminum.

In contrast, 7075 aluminum serves best in the conditions mentioned below:

  • If the product needs to withstand high friction, this alloy can be a perfect material.
  • The parts that demand a high strength-to-weight ratio are usually made of 7075 aluminum.
  • If you want your product to withstand high temperatures or heat, this alloy will definitely work best for you.

 

Conclusion

Generally, 6061 aluminum is excellent for meeting industrial manufacturing requirements for producing most objects. However, 7075 aluminum is preferable for rare applications that demand outstanding strength and hardness, such as aerospace, military, and high-end items. Now, selecting a suitable aluminum alloy according to your project requirements is up to you. Still, if you find it challenging, JIAHUI is here to assist you. Our vetted experts will help you choose between 7075 t6 vs 6061 t6 Aluminum according to your project.

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