Aluminum Alloys
These days it is difficult to read about motorcycle parts without being swamped with advertisements talking about "billet aluminum" or "aircraft aluminum". What does all of that mean, and why is it important?Background
First, a little background information. Aluminum is a common chemical element, making up about 8% of the Earth's crust. However, until the invention of modern extraction techniques during the 20th century, aluminum was extraordinarily expensive due to the difficulty in purifying it. Pure aluminum, however, is a very soft metal which cannot be used for high-stress parts. For this reason, aluminum is alloyed (mixed) with other materials in order to form a strong metal that can be used for high stress parts. Today, pure aluminum is very rarely used. "Aluminum" parts are almost always an alloy of aluminum and other metals. There are literally hundreds of different alloys which are optimized for various applications. Each alloy has a numerical designation. For example, "6061". "6061" describes to engineers what the exact chemical makeup of the alloy is—and this is important becasue different alloys have very different characteristics. After all, a beer can is not made from the same "aluminum" as the wing spars on a 747.Common Alloys
Here are some of the most common and important alloys:1060
1060 Aluminum is also known as "commerically pure aluminum". It consists of 99% (or more) elemental Aluminum with only traces of other elements. 1060 aluminum is very weak and is difficult to machine, and thus is rarely used.2024
2024 alloy is the original "aircraft aluminum"—also known as Duralumin or "Dural". This was the first "high strength" aluminum alloy to be developed. It was invented in Germany in 1903 and it gained fame as the material of choice for lightweight machinery, especially airships and airplanes. 2024 was used in all fighter aircraft in WW2, and continues to be used in many aircraft applications today. While 2024 is among the stronger alloys, it is susceptible to corrosion. For this reason other alloys are commonly used in its place in the aircraft industry today.6061
6061 alloy is an extremely common modern aluminum alloy. It has good strength, it is easily machined, and it resists corrosion. It is also lower cost than most other alloys. Due to these factors it is extremely popular for aftermarket parts used in motorcycles. If you see a part labeled "billet aluminum" or "aircraft aluminum" but the alloy is not specified, then it is safe to assume that it is 6061 alloy. Note that this is misleading as 6061 alloy is generally NOT used for aircraft applications as there are other alloys which have better mechanical properties. Despite this, many people will call 6061 "aircraft aluminum" anyway. We use 6061 Alloy only for low-stress parts where unusual strength is not required, such as spacers and license plate brackets. However, many companies do use 6061 for high-stress parts simply becasue it is inexpensive, easy to machine, and it also lets them put the "aircraft aluminum" name on their parts—even though 6061 is not a high performance alloy at all.7075
7075 alloy can be thought of as the modern replacement for 2024. It is commonly used in aircraft and aerospace applications. 7075 is stronger than 2024 and is also has much better corrosion resistance. 7075 is, however, much more expensive than general-purpose alloys such as 6061, therefore it is rarely used in motorsports components. Note that 7075 Aluminum has a very similar strength-to-weight ratio to 6AL-4V Titanium. TPO Parts uses 7075 alloy for many different parts where a high strength-to-weight ratio is important, such as our clutch spring retainers, GP shift kit, and aluminum hardware (fasteners, nuts, and stressed hardware).7068 - The Ultimate Alloy
7068 alloy is a very modern development. It was developed circa 2000 by Tennalum, Inc. for aerospace and military applications. 7068 has an extremely high tensile strength, and this enables it to exceed the strenght-to-weight ratio of nearly all engineering alloys. 7068 alloy is greater than twice the yield strength of most common aluminum alloys. It has 33% better strength to weight ratio than 7075 alloy (true aircraft aluminum), and 28% better performance than 6AL 4V Titanium. For many applications, there is no better alloy, not even Titanium.
TPO Parts is pioneering the use of 7068 alloy for motorcycle applications. We take full advantage of its fantastic mechanical properties in our lightweight front axles, clutch hub brace, and brake rotor buttons. 7068 alloy is expensive and tricky to machine compared to more common alloys. But, it delivers weight savings that no other alloy can match. When you see a TPO Parts-engineered 7068 part, you know you've reached the pinnacle of performance. 7068 parts outperform stock, outperform other aluminum alloys, and even outperform Titanium.
