If you aren’t sure what the difference between 6061 and 7075 aluminum is, you came to the right place. Picking the wrong alloy out of these two might mean that your project can’t physically be machined. In this guide, we’ll explain why that’s the case. We’ll talk about 6061 and 7075 aluminum and compare both options.
What The Aluminum Alloy Number Means
When you’re shopping for wrought aluminum alloys, you’ll always notice a four-digit code. In this case, we’re looking at 6061 and 7075. They might look like random numbers, but they tell you a lot about the aluminum alloy.
Each digit of the code tells you something about the mixture of metals, since these are alloys — in other words, they’re not pure aluminum and they’re mixed with other metals.
The first digit tells you what the principal alloying element is, or the main element. The second option tells you if there’s any modification to the alloy, and the last two digits are almost a serial number for all alloys within that family.
If the second digit is a 0, that means there is no change to the base alloys used.
Let’s talk about an example. 1050 aluminum is a type of “pure” aluminum which is actually around 99.5% aluminum by content. The first digit, “1”, tells you that this alloy is within the “pure aluminum” family. The second digit, “0”, tells you that there’s no change to the base alloy (aluminum). The third and fourth digits, “50”, are simply the serial code of this specific type of pure aluminum.
Compare that to an 1100 alloy of aluminum. It’s in the same “pure aluminum” family since the first digit is still “1”. However, this option has a “1” in the second digit, meaning there’s a change to the base alloy. In this case, copper is added to the mixture making up 0.1% of the total contents. The last two digits are “00”, again just giving a serial number to this specific alloy.
The same logic is used from 1000-series to 8000-series of aluminum. More info can be found in this guide.
What Is 6061 Aluminum?
Now that we know more about the four-digit index, you will notice a “6” and “0” in the beginning of this alloy. The “6” family uses magnesium and silicon as the base, and the “0” tells us that this alloy is unchanged. The 61 is just the serial number for this alloy.
In a machine shop, 6061 is one of our favorite aluminums to use. It’s a general-use alloy that’s incredibly easy to machine, weld, and assemble. As a designer, you might default to 6061 aluminum if you don’t have specific use cases that are more restrictive.
This is the most popular alloy of aluminum used on the market. It has a decent hardness, tensile strength, density, and cost associated with it as well.
What Is 7075 Aluminum?
A 7075 aluminum uses a non-changed base of zinc as its main component. Zinc is a lot stronger and harder than the magnesium and silicon used in the 6000 family of aluminum. As a result, 7075 aluminum is significantly stronger than 6061 aluminum.
You’ll usually see 7075 used in aerospace and defense industries — two places where the strength and density of a material are critical.
The additional zinc also makes 7075 aluminum very good at handling stress and preventing fatigue over time. If you’re looking at an application where a part is constantly being moved, used, or loaded, then it’s worth the upgrade to 7075.
The Main Difference Between 6061 and 7075 Aluminum
We hinted at a lot of these differences already, but let’s be more specific. This section is all about the exact differences between 6061 and 7075 aluminum.
Strength
The biggest difference between these two alloys is the strength that they both can handle. If you want to talk about numbers, the yield strength of 6061 aluminum is 35,000 psi, while 7075 aluminum has a yield strength of 65,000 psi. No, that’s not a typo — 7075 is nearly twice as strong as the more common 6061 aluminum alloy.
Machinability/ Weldability
Since 6061 is softer and not as strong, it’s a lot easier to work with. What does that mean? It means that 6061 aluminum is significantly easier to machine, weld, bend, and assemble. With 7075, we have to change our machine speeds and be a lot more careful. Even with this extra care, it’s easy to crack a piece of 7075 when we’re welding or bending it.
This also means that you can expect higher quotes from machine shops whenever you spec 7075 as your aluminum alloy of choice.
Availability
If you look at a metal distributor, you’ll find countless 6061 options in their catalog. They make 6061 aluminum in a wide range of thicknesses, lengths, and widths. This is because it’s the most common alloy of aluminum, and it’s incredibly popular.
7075 has a smaller range of options. There are still plenty to choose from, but it might mean longer lead times, or waiting for a custom order.
In general, 6061 is more widely available.
Cost
Since 7075 is harder to work with, more difficult to source, and stronger, it shouldn’t be a surprise that 7075 is a lot more expensive. Not only is it more expensive for us to buy it, but you’ll notice higher quote prices when you use 7075 in a project instead of 6061.
This is why we suggest using 6061 in every case where you don’t have specific strength requirements or a need for extra corrosion resistance.
Conclusion
Picking the right aluminum alloy can work wonders for your next project. If you’re between 6061 and 7075 aluminum, we hope this guide helped you make your final decision. To start machining your parts today, reach out to our team at Rapid Axis. We are a full-service machine shop that can handle a wide range of services and material options. Get a free quote today.