Whether you’re in manufacturing or a DIY enthusiast, you’ll have been confronted with making a difficult decision between two versions of the same materials at some point. Such situations can happen with aluminum.
Aluminum is a top-choice material in many industries and is loved for its lightweight, durability, and ability to be shaped in numerous ways. It’s also used in almost all industries from building aircraft to smartphones. But here is the interesting twist: not all aluminums are created equally. There are distinct characters based on specific parameters for both aluminum 6061 and 7075. Chemical, mechanical, and fabrication considerations are the properties we’ll break down in this guide. Frankly, you should get all the knowledge you require to choose the most suitable aluminum for your next project at the end of this article. So, let’s get down to it.
What is Aluminum 6061 And 7075?
Individuals in manufacturing industries understand the importance of choosing the right grade of aluminum from the start. It allows them to avoid any mistakes that can be awfully expensive to fix down the line. While aluminum is one of the most widely used materials in the manufacturing industry, given its high strength-to-weight ratio, its two most popular grades remain aluminum 6061 and 7075. Let’s look at these aluminum alloys in detail.
6061 Aluminum Grade: Known for its superb weldability, excellent anti-corrosion properties, and brilliant surface finish, this heat-treated aluminum alloy is often used in places where structural integrity of the product is a priority. As a versatile material, aluminum 6061 is highly machinable thanks to its high formability which allows professionals in mold manufacturing to form different shapes using methods like forging, rolling, and extrusion. Also, its dazzling surface finish gives it an impressive aesthetic appeal which makes it suitable for design components. It is used extensively in the marine, aerospace, and automotive industries for exceptionally reliable parts and equipment. Furthermore, its anodizing ability makes it an excellent choice where adhering to color codes and specifications are compulsory.
7075 Aluminum Grade: This aluminum grade has less aluminum but more magnesium and zinc than the 6061 version which gives it more strength. It is often applicable in situations where engineers and metallurgy professionals need to overcome high stress. These situations include the manufacture of equipment and machinery used in the sport, military, and aerospace industries. Its hardness and strength also make it a suitable material for manufacturing molds since it ensures dimensional stability. However, its downside is its machinability given its hardness which makes it difficult to work it with a machine. Consequently, working aluminum 7075 requires special tools and equipment as well as employing sophisticated methods to achieve the desired finish.
Both grades of aluminum are excellent choices for the industrial production of components that are durable, strong, and corrosion resistant. Yet, one will be more suitable than the other depending on the specifics of the project.
The difference: Aluminum 6061 and Aluminum 7075
Now that the general definitions and characteristics of each aluminum grade are out of the way, it’s time to look at their properties in detail. However, to fully understand their uniqueness and difference we will consider critical chemical and mechanical properties like yield strength, thermal conductivity, machinability, electrical conductivity, and elasticity, among others.
- Alloy Series
The first distinguishing factor for most metallurgy and materials professionals is the series of aluminum since each series has its own defining characteristic and behavior.
For the 6061 aluminum grade which forms part of the 6,000 series, its characteristic is typical of the series it belongs to. This series is identified with its anti-corrosion properties along with its outstanding formability and weldability. These properties make it appropriate to produce most multipurpose aluminum components used in many industries ranging from electronics to automotive.
In contrast, 7075 aluminum is often identified with the 7,000 series characterized by fatigue resistance, high strength, and corrosion resistance. With its ability to undergo heat treatment, the aluminum 7075 is often found in industries that require materials that can resist a lot of stress and load impact such as in aerospace and in military hardware production.
- Chemical Components
The composition of alloys often accounts for their unique abilities, especially for alloys like aluminum, considering that a slight reduction in one constituent can significantly affect its suitability in an area. Hence, chemical composition has a massive impact on the difference between these alloys. Aluminum 6061 is composed of 97% aluminum and 1% magnesium, with copper, silicon, iron, zinc, and titanium, having less than 1% each and chromium constituting the least amount at 0.04%. Aluminum 7075 on the other hand has 90% aluminum, 5.6% zinc, 2.5% magnesium, and 1.6% copper, with 0.23% chromium. These differences in the chemical composition of the two alloys make for their different characteristics and distinctive uses.
- Mechanical Properties
For engineers and manufacturing professionals, the mechanical properties of a material often indicate from the early stage of design its tolerance limits and suitability for a project. Parameters like yield strength, elasticity, and machinability often determine the differences between various materials and aluminum 6061 and 7075 are not exempted. Let’s see the differences between these aluminum alloys using different mechanical properties.
- Yield Strength Comparison
When materials are loaded beyond a certain limit, they begin to deform at which point they would have reached their yield point. The greater the yield strength of a material, the longer it takes to deform under load applications. Aluminum 7075 has more yield strength than 6061. Consequently, aluminum 7075 can resist more stress and will not deform under the same load that can cause deformation for aluminum 6061. It’s no wonder aluminum 7075 components often come under heavy stresses during their lifetime.
- Elasticity Comparison
The ability of a material to return to its original shape and size after experiencing some elongation due to load application is known as elasticity. This property is most critical for load-carrying elements in a structure. Aluminum being a structural material is often analyzed using this parameter. However, aluminum 6061 with a young’s modulus of 10,000 ksi does better in this area than aluminum 7075 with a young’s modulus of 10,200 ksi. The implication of these values is that aluminum 6061 will return to its original shape and size when subjected to the stresses that can cause aluminum 7075 to remain permanently plastic.
The ability to operate on a material using manufacturing techniques like CNC machining can be critical, especially in production where machining can help in rapid production. Cutting and shaping aluminum 6061 is easier using a machining procedure than aluminum 7075. The reason for this difference is the lower strength and hardness of 6061 compared to that of 7075. Cutting aluminum 7075 is more difficult and sometimes requires unconventional techniques and tools to achieve the required shape since 7075 is harder than 6061.
- Thermal Conductivity
A huge requirement for electronic manufacturing, especially for components like heat sinks, is thermal conductivity. These components are mostly responsible for dissipating the heat generated within the internal panels of the device. And having good thermal conductivity helps to effectively dissipate the heat produced. There is only a marginal difference in their thermal conductivity which means they both dissipate heat generously. Only that 6061 aluminum is slightly better at heat dissipation.
- Electrical Resistivity
While conductivity measures the ease of electrical flow within a material, resistivity measures the resistance of current flow within the material. Aluminum 7075 is a little more resistive to current flow than 6061 which indicates that aluminum 6061 will serve as a better electrical material than aluminum 7075.
- Material Hardness Comparison
The indication of a material’s durability is mostly measured based on its hardness as this indicates the material’s ability to endure loads and rough handling without much tear or wear. Materials’ hardness is also measured based on the impression left on their surface after the application of a series of loads, especially when using a standard hardness test. Incidentally, aluminum 7075 is harder than its 6061 counterparts as given by the standard Brinell test which shows a hardness value of 150 and 95 for aluminum 7075 and 6061 respectively.
- Common Applications
The above-highlighted properties give an indication of areas where each aluminum alloy version will excel. Even for areas like thermal conductivity where they are marginally different they still serve better for different areas where these parameters are paramount.
- 6061 Aluminum Applications
It’s no surprise that aluminum 6061 will be applicable in areas like automotive manufacturing and consumer goods packaging where formability and weldability are key major factors. Its ability to easily form different shapes and sizes while maintaining structural integrity is highly desirable in mold design for auto parts. Also, its corrosion resistance properties make it appropriate for marine applications including component parts for ships and vessels.
- 7075 Aluminum Applications
Such industries as aerospace, construction, and military hardware manufacture use aluminum 7075 to produce components that can withstand high pressure per unit area without yielding or deforming and with little or no wear and tear.
- Fabrication Considerations
Fabrication for both aluminum versions follow specific techniques and procedures seeing that they are different in many ways. For instance, an aluminum 6061 that is softer with high formability and weldability will do well with the machining fabrication and welding process. Also, extrusion fabrication methods are appropriate for certain dimensions and sizes. Again, for finishes that require specific color procedures like anodization, aluminum 6061 will fit perfectly.
In the case of aluminum 7075 with a harder, less ductile property, fabrication methods other than machining and welding will be suitable. This alloy will require a great deal of meticulousness and precision to avoid cracks and other forms of manufacturing errors.
In any case, the best fabrication method will depend largely on the material properties and other factors including the speed of manufacturing like in the case of rapid prototyping, and budget.
Ultimately, understanding the uniqueness of each version of aluminum alloy will help you decide better on the best one to use for your project at any time.
How about Other Properties?
The considerations highlighted previously are the major selection criteria for the type of aluminum alloy to use in your project. However, they are not the only factors to consider in your material selection process. There are other factors that are not related to strength but are equally important.
Corrosion Resistance Comparison
While both 6061 and 7075 aluminums have good anti-corrosion properties, they still have their limitations. 7075 aluminum has less anti-corrosion properties than 6061 aluminum, yet it is able to survive harsh environments where the corrosion is really high over a long period.
For 6061 aluminum which has more corrosion resistance, its limitation is that it can survive harshly corrosive environments for long. Fortunately, protective coatings can help increase the defense against highly corrosive surroundings.
With 6061 aluminum which has high weldability its application for most manufacturing processes requiring welding is often straightforward. However, due to 7075 aluminum’s low weldability, it’s often not the first choice for most operations requiring welding. Still, advanced techniques for welding 7075 aluminum have been used by highly experienced welding professionals.
There are use cases that subject materials to extreme temperatures and the ability to withstand such heat is required in using a material for the manufacture of a component. While 7075 aluminum can withstand more heat as a finished component, it will take more heat to process it during the manufacturing process.
Weight is a critical consideration during the design phase as some use cases require less weight to be effective. In this case, the 7075 aluminum is heavier with a density of 2.8 g/cm 3 while 6061 aluminum has a 2.7 g/cm 3. but while the difference in weight might not be much it can add up pretty quickly if the volume of material required is more.
The cost is sometimes the most crucial factor of production as your budget often limits your option even if you desire higher quality. 6061 is less expensive since it is softer and requires uncomplicated techniques and tools during production. The reverse holds true for 7075 aluminum which often requires more sophistication during production and there lies the increased cost.
For 6061 VS 7075 Aluminum, Which One Is Better?
In a nutshell, several factors determine the suitability of a material for a project including its strength, durability, machinability, and composition and aluminum 6061 and 7075 are not exempted from this criteria. However, other factors like cost, weight, corrosion resistance, and aesthetic and color specifications can have a significant effect on your choice. Nevertheless, the greatest decision will often be the individual project’s requirement.