The rising popularity of aluminum, a trend that has continued for decades, began with the diversification of alloys in the early 20th century. In particular, the bourgeoning aircraft industry of the 1930’s spurred the rapid development of new alloys that were extremely light and extremely strong, perfect for airplanes. Two of those new alloys were 6061 and 7075.
Among the most commonly used aluminum alloys, they each have their own unique characteristics. Understanding the differences between them is important for industry decision makers who are tasked with finding the perfect material for their particular applications. Choosing the right alloy can help manufacturers save both time and money while better meeting the demands of their customers.
What are 6061 and 7075 composed of?
Both 6061 and 7075 aluminum alloys were developed in the 1930’s for the aircraft industry. 6061 was first introduced in 1935 and was one of the first commercially available alloys. The main two elements in its chemical makeup are magnesium and silicon. Magnesium is added to aluminum to increase its strength. The silicon is used to reduce the melting temperature. Individually, magnesium and silicon create aluminum alloys that are unable to be heat-treated in an effective manner. By combining them however, the new alloy responds well to heat treatment. The other trace elements in 6061 include chromium, iron, and copper.
7075, on the other hand, was developed in 1936 by Sumitomo Metal Industries, a Japanese manufacturer that was looking for solutions to build cheaper and lighter aircraft. It was able to create lightweight frames that offered superior handling and greater flight range. Its main alloying agent is zinc, and it has one of the highest strength to weight ratios of the aluminum alloys. It also includes trace amounts of silicon, iron, manganese, and titanium.
What are their specific characteristics?
6061 aluminum is known for its superior structural strength and toughness. It provides for a good surface finish while offering excellent corrosion resistance when exposed to atmosphere and seawater. It is also considered to have good machinability and can be easily welded and joined. Once it has been welded, 6061 may see a reduction in strength, but it can be heat-treated again in order to restore strength.
Its detailed mechanical properties are as follows. For its tensile strength, 6061 (T651 Bare) is listed at 45,000 psi, with a yield point of 40,000 psi. The Brinell hardness is rated at 95. The elongation at break is 12% and shear strength is 31,000 psi. 6061 has a thermal conductivity of 170 W/m-K. And finally, its strength to weight ratio is rated at 115 kN-m/kg.
7075 aluminum alloy is perfect for applications where high strength is essential and good corrosion resistance is less important. It is known to have a high strength to weight ratio and certain tempers offer decent resistance to stress-corrosion cracking. 7075 is able to match most steel alloys in terms of strength. In general, it does not offer good weldability. It can be forged in temperatures ranging from 700 to 900 degrees Fahrenheit, as long as it is subsequently heat-treated.
As for its detailed characteristics, 7075 Aluminum (T651) features a tensile strength of 83,000 psi, with a yield point of 74,000 psi. The Brinell hardness is rated at 150, with the elongation at break being 10%. It offers a shear strength of 48,000 psi. Its thermal conductivity is rated at 130 W/m-K with a strength to weight ratio of 196 kN-m/kg.
What all of this amounts to is that 6061 is generally more versatile than 7075 and thus can be used in a greater variety of applications. On the other hand, 7075 is one of the strongest aluminum alloys available. While 7075 is less workable than 6061, if your greatest consideration is strength, then 7075 is probably the better choice.
What common applications use 6061 and 7075?
As previously mentioned, 6061 aluminum alloys offer a great deal of versatility, and thus are found in a wide range of applications. 6061 is commonly employed as a construction material, in particular in the automotive industry. It can also be found in motorcycles, boats, bicycles, scuba tanks, camera lenses, fly fishing reels, firearms, and electrical fittings. In the food industry, many aluminum cans are made from 6061. Docks and gangways are often constructed from this alloy. This is all in addition to the many aircraft parts that still use 6061.
7075 alloys, by comparison, tend to be used in high performing products such as marine, automotive, and aviation transport. This is due to their high strength-to-weight ratio. Other products that use 7075 include rock climbing equipment, bicycle components, inline skates, and hang gliders. A number of firearms incorporate 7075 alloys into their design, including M16s. Gun manufacturers such as Desert Tactical Arms, SIG Sauer, PGM, Texas Black Rifle, and Glock Micro Company all use it in their products. Other applications include lacrosse sticks, camping utensils, yo-yos, and mold tool manufacturing. Hobby grade remote control models often use both 7075 and 6061.
What do you need to consider when selecting an aluminum alloy?
Manufacturers need to take many factors into consideration before settling upon a particular alloy. These items belong on any checklist and will help you determine which alloy is right for you. Questions you should ask include:
- Is formability an important consideration in your application?
- Do you need an alloy that is weldable?
- Will machining be an important factor?
- Does your application require good corrosion resistance?
- Will you be using heat-treating in your application?
- Is strength a key consideration?
Summary
By going through the above checklist, you can quickly narrow down what is most important for your particular application. At Clinton Aluminum, we pride ourselves on our ability to work with manufacturers to identify what is most essential to them and their clients and select the right alloy for the job.
As the Midwest’s number one supplier of aluminum, Clinton Aluminum has the experience and resources to help ensure your applications are successful. Contact us today to speak with one of our knowledgeable and friendly representatives.
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