When it comes to choosing a metal for high-strength, low-weight applications, aluminum 6061 is one of the highly sought-after alloys, especially in North America. Additionally, it displays excellent corrosion resistance, coupled with high machinability and weldability, making it ideal for a lot of applications.
However, there are certain application restrictions. For instance, unlike 5052 alloys, 6061 is not ideal where a larger bending radius is required. Similarly, if it’s important to have high yield strength, aluminum 7075 would be a better choice than aluminum 6061.
Thus, it’s important to understand the most essential aluminum 6061 material properties before using it for your application.
Essential Aluminum 6061 Material Properties
Below, we detail some of the most important material properties of aluminum 6061 that could affect whether or not it would be beneficial for your fabricating or machining requirements.
Aluminum 6061 contains magnesium and silicon as major alloying elements, as well as manganese, iron, titanium, copper, and chromium. The exact nominal composition is as follows:
- Aluminum 97.9%
- Silicon 0.6%
- Magnesium 1.0 %
- Chromium 0.20%
- Copper 0.28%
While copper improves the mechanical properties of aluminum 6061 as well as its response toward artificial aging, chromium offsets any adverse effect of copper on the aluminum 6061’s ability to resist corrosion. The high alloy content in 6061 increases its quench sensitivity.
The tensile strength of 6061 represents the ability of the metal to withstand a pulling force, measured in force per cross-sectional area. The tensile strength of 6061 varies with changes in heat treatment. Different 6061 tempers have different tensile strengths (for example, 45 ksi for 6061-T6). Though the tensile strength of 6061 is half that of 7075, it is still strong enough for many constructional applications.
The ultimate compressive strength of aluminum 6061 changes with different composite materials. For example, by increasing the weight percentage of composites such as graphite and fly ash particles, the compressive strength of the alloy increases. On the other hand, an increase in reinforcement particle size marks a decrease in percent improvement.
The T6 temper of aluminum 6061 offers the highest precipitation hardening among all of the tempers and thus has a maximum yield strength of 240 MPa. However, again, the value may change with the type of composition. While the hardness of aluminum 6061 is significantly improved with an increased content of albite particles, it displays the opposite phenomenon with graphite reinforced composites.
Aluminum 6061 shows significantly higher fatigue ductility than any other alloy. It has also been noticed that the 6082-T6 alloy is comparatively less ductile than the 6061-T651 alloy because it has a slightly higher content of silicon and magnesium. Also, the ductility of the composite decreases with an increase in the weight fraction of hard particles such as fly ash.
Corrosion resistance is one of the most valuable aluminum 6061 material properties. In the presence of air or water, aluminum 6061 forms a protective oxide layer against atmospheric corrosion. However, due to the presence of copper, the degree of resistance is comparatively less than aluminum 5052. The 6061 alloy is ideal for applications requiring resistance against nitric acid, ammonia, and ammonium hydroxide. Though it may develop pitting with alkali soil, an additional protective layer coating can help.
The table below lists the maximum limit of some of the most important aluminum 6061 material properties discussed above.
|Ultimate tensile strength||45,000 psi|
|Yield strength||40,000 psi|
|Shear strength||30,000 psi|
|Melting point||1,080–1,205 °F|
|Modulus of elasticity||10,000 ksi|
|Specific heat capacity||0.214 BTU/lb-°F|
|Thermal conductivity||1,160 BTU-in/hr-ft²-°F|
|Coefficient of thermal expansion||13.1 µin/in-°F|
6061 Material Properties Under Heat Treatment and Temperature Change
To further improve their desirable machining characteristics, aluminum 6061 alloys are heat treated and are available in different tempers, as listed below:
6061-F: As Fabricated
These are semi-furnished alloys with no special control over thermal treatment. The semi-furnished alloy further goes through shaping, finishing, or thermal process to achieve other finished forms or tempers.
At some point during the process, the alloy is annealed to improve workability and maximize ductility and toughness. It is best suited for forming and welding operations but has poor machinability.
6061-W: Solution Heat-treated
Just like 6061-F, these alloys also don’t have any published standard property limits, as they age naturally and spontaneously after solution heat treating. The yield strength grows eventually until it receives further treatment to stabilize its properties.
6061-Tx: Thermally Treated
Here, the alloy, post-solution heat treatment, goes through quenching and either natural or artificial aging. As a result, it achieves commercially useful strength and toughness. An additional digit added to the temper indication specifies any special treatments it received.
Ideal Application Areas of Aluminum 6061
Aluminum 6061 is available in the form of bar stock, sheet, plate, and round stock.
Due to their good thermal and electrical conductivity, aluminum 6061 plates are used as heat radiators in engines to offer maximum cooling efficiency. Additionally, the lightweight feature makes aluminum 6061 ideal for various aerospace and general transport applications. In many shops, the 6061-T6 alloy is used as the tread plate to support most processing techniques. The combination of exceptional resistance to corrosion, weldability, and strength makes 6061 plates useful for common applications, including truck beds, stairs, support structures, ramps, and catwalks.
Aluminum 6061 bar stock finds a wide range of heavy-duty structural applications involving truck frames, rivets, motorboats, and rail coaches. The presence of magnesium and silicon makes the structures immune to stress, cracking, and corrosion.
Reliable Local Supplier of Aluminum 6061 and Other Alloys
With so many different tempers available, choosing the right aluminum 6061 alloy for the required application can be very difficult. Industrial Metal Service specializes in offering helpful guidance for selecting the right temper and supplying metals to your workshop, anywhere in the San Francisco Bay Area and beyond. We stock a wide range of metal alloys, including mill-sourced new metals and verified remnants, and supply them to U.S. customers who don’t have the benefit of a local supplier.