If you need metal for a project, you’ll quickly find that aluminium alloys are some of the best materials out there. They are a great mix of strong, lightweight and easy to work with.
Many people talk about the debate between 6061 and 7075 aluminium. These two materials are very well known in the world of manufacturing, but they can’t be used for the same things. At first glance, they may look similar, but they are very different.
Choosing the right material is an important factor in the success of any project. You should know what characterises each of these alloys.
In this guide, you’ll learn everything you need to know about 6061 and 7075 aluminium, including when you should use the two materials and what sets them apart.
What is 6061 Aluminium Alloy?
6061 aluminium is the best all-round metal. It is often referred to as the “jack of all trades” for good reason. It is versatile and has excellent mechanical properties.
It’s even more popular because it’s not too expensive, which is always a plus. This alloy has good tensile strength and high corrosion resistance. It is also easy to cut and shape, which means it is easy to machine.
Manufacturers like to use it for many things because it is so easy to work with. You’ll find it in bicycle frames, electrical equipment, car parts and even pipes. It’s a reliable and affordable choice for a wide range of applications.
What is 7075 Aluminium Alloy?
Now let’s talk about 7075 aluminium, which is the main part. Zinc is the main alloying element in this alloy, which belongs to the 7000 series.
7075 is known for one thing above all: its strength. Its strength makes it a popular choice for industries where failure is not an option, such as aerospace and defence.
It is also highly resistant to fatigue, meaning it can be heavily loaded over and over again without breaking. 7075 costs more than 6061, and it’s also a little more difficult to weld. You’ll often find it in high-stress areas such as aircraft frames, high-end bicycle parts and plastic moulding tools.
The Difference Between 6061 and 7075 Aluminum Alloy
So, we know one is a versatile all-rounder and the other is a high-strength specialist. But let’s dig into the nitty-gritty details. What really is the difference between these two common types of aluminium?
Alloy Series and Chemical Composition
The first clue is in their names. The numbers aren’t random; they’re given out by the Aluminum Association and tell you what family the alloy belongs to. 6061 aluminum is from the 6000 series. For this series, the primary alloying elements are magnesium and silicon.
On the other hand, 7075 is a 7000 series alloy. Its principal alloying elements are zinc and copper. The chemical composition is what gives each alloy its unique set of properties. For instance, 7075 has a much higher zinc content and more copper than 6061, which is a key reason for its different behaviour.
Mechanical Properties
This is where you can really see the differences. The way a metal reacts to force is determined by its mechanical properties. 7075 has a much higher yield strength than 6061, which means it can withstand more stress and impact before bending or changing shape.
This is why it is used in high-stress situations. It gets its strength from its unique chemistry and the fact that it has been heat-treated. 6061 is no pushover, however, as it has a yield strength of 276 MPa.
Both are good at conducting heat. So when it comes to thermal conductivity, they are both good. But 6061 conducts heat better and is therefore the better choice for things like heat exchangers that need to dissipate heat quickly. Also, both have low electrical resistance, but 6061 is slightly better at conducting electricity.
6061 can withstand higher temperatures because it has a higher melting point (582–652°C) than 7075 (477–635°C). 7075, on the other hand, reacts very well to heat treatment, which makes it harder.
If you look at the most common types, known by the common designations 6061 t6 and 7075 t6, the difference in strength becomes very clear.
Machinability
Machinability is about how easily a material can be cut, drilled, milled or moulded. This is an area in which the two alloys differ significantly.
As a rule, 6061 is much easier and quicker to machine. Its lower hardness means that tools last longer and the process is smoother. This is why it is a popular material for machining parts with customised shapes.
7075 is stronger and harder due to the addition of copper and magnesium, making it more challenging to machine. It’s by no means impossible, but it requires more advanced tools and techniques to get the job done right, especially when making complex shapes.
Anodising
Anodising is a nifty trick. It’s an electrochemical process used to create a durable, corrosion-resistant and decorative metal surface. Essentially, you create a tough protective layer by thickening the natural oxide on the surface. An oxide layer created by this process is very strong.
Both 6061 and 7075 can be anodised to create a clear oxide layer for protection. However, there is a small catch with 7075. Due to its higher zinc content, there is a possibility that it will turn brown during the anodising process if there is too much zinc present.
Welding performance
If your project involves welding, this is a crucial point. 6061 is considered to have excellent weldability. It can be welded using a variety of methods and handles heat well, making it perfect for fabricating welded assemblies.
7075, on the other hand, is generally not considered to be weldable. The high proportion of zinc in its composition can lead to major problems such as hot cracking, resulting in weak or faulty joints.
You can improve its weldability by subjecting it to an annealing process that softens the metal. But even then, it must be heat-treated again after welding to regain its strength.
Cost consideration
Cost is always a factor. Due to its specific chemical composition, which contains more expensive elements such as zinc, 7075 is the more expensive of the two alloys. The special treatments that are sometimes required, such as advanced welding techniques, also increase the final price.
6061 is the less expensive option. Its lower cost and the fact that it is easier and cheaper to machine make it the first choice for many general-purpose applications.
Corrosion resistance
When it comes to standing up to the elements, 6061 has the upper hand. It is more resistant to corrosion than 7075, and the reason for this is quite simple: the copper content. 7075 has a significantly higher percentage of copper in its mix.
Copper reacts more easily with the environment, which means that corrosion is more likely to occur. This makes 6061 a better choice for applications in wet or humid environments, such as marine fittings.
Fabrication considerations
Fabrication involves all the processes of making something, from moulding and cutting to joining. Overall, 6061 is easier to work with.
This is due to its lower hardness and tensile strength. It is softer, which allows for good machinability, and its lower strength gives it good mouldability, meaning it is easier to bend and shape.
While both materials can be joined with adhesives or by soldering, the big difference is welding. As we have seen, 6061 is weldable, whereas 7075 is not.
Applications of 6061 Aluminium Alloy
The versatility of 6061 means you’ll see it absolutely everywhere. It’s a true workhorse among structural materials.
Building products: Its combination of strength, light weight and corrosion resistance makes it an ideal material for structural components.
Automotive parts: Used in various components, including frames and bus bodies, where durability and weight are important.
Electrical products: Its good conductivity makes it suitable for electrical fittings and connectors.
Bicycle frames: Many bicycle frames are made from 6061 because it offers a good balance between strength, weight and cost.
Tubing: Its corrosion resistance and workability make it a solid choice for piping systems.
Applications of 6061 Aluminium Alloy
7075 is reserved for applications where maximum performance is required. Its applications are often in environments with high demands.
Missile parts: For military applications such as these, the high strength-to-weight ratio is critical.
Aircraft components: As aircraft material, they are used for frames and other structural parts that are exposed to high loads. Its high fatigue limit is crucial here.
Gear wheels and shafts: Their hardness and high wear resistance make them ideal for these components.
Fuse parts: Used in applications where reliability under stress is non-negotiable.
6061 vs. 7075 Aluminium: Which Material Should I Choose?
Choosing between different aluminium alloys can feel difficult. Ultimately, your decision will depend on the specific requirements of your project. You need to think about the application, the manufacturing process and, of course, the cost.
Here’s a simple breakdown to help you decide.
You should lean towards 6061 aluminium if:
Your project requires a lot of machining or complicated moulding.
You need to weld parts together.
The part will be exposed to moisture, and corrosion resistance is important.
Cost is an important consideration, and you need a budget-friendly solution.
You should choose 7075 aluminium if:
An extremely high strength-to-weight ratio is a top priority.
The part will be exposed to high heat or needs to be heat-treated for maximum strength.
The part must be able to withstand high friction and wear.
Cost is a secondary consideration, and performance is everything.
Conclusion
So, there you have it. In the debate between 6061 and 7075 aluminium, there is no single winner. Both are fantastic alloys, but they are designed for different tasks.
6061 is your versatile, reliable, and affordable friend, perfect for a wide range of projects that require good all-round performance.
7075 is the high performance specialist you turn to when you need ultimate strength and hardness and are willing to pay a little more for it.
The key is to look at the requirements of your project. Think about strength, weldability, corrosion and cost. When you weigh up these factors, you’ll know exactly which of these excellent construction materials is right for you.