If you’re an engineer, machinist, or designer looking to work with 6061 aluminum, you must first understand its characteristics. This will help you get the best performance from the material. In this article, we’ll go over everything you need to know, from its key applications to its properties.
What Is 6061 Aluminum?
A6061 aluminum is an alloy that’s favored for its weldability, corrosion-resistance, and strength, particularly after heat treatment. It’s not a pure metal, as it contains a mixture of other elements. They are magnesium, silicone, copper, and chromium.
You may also see it written as A96061, which is its Unified Numbering System (UNS) designation.
Common 6061 Aluminum Temper Designations
When you apply certain metallurgical processes to 6061 aluminum, you produce different tempers. These processes include solution heat treatment, quenching, artificial aging, annealing, and stress relieving. Below are five of the most common 6061 aluminum tempers, how they’re made, and why they’re useful.
6061-O
You can create this fully softened type of 6061 alloy through annealing. First, you must heat the material to around 415°C (775°F). Then, slowly cool it.
The result is a ductile alloy that you can easily bend, roll, or deep draw. Its minimal internal stresses make it extremely workable for parts that you want to form before hardening.
6061-T4
You can make the T4 temper by solution heat-treating 6061 aluminum at approximately 530°C (985°F). This dissolves the various elements in the alloy. You must then rapidly cool it in water. This is known as quenching, which essentially freezes the structure.
Next, you need to naturally age it at room temperature. During this phase, the dissolved elements (like Mg and Si) precipitate out of the solution. They form tiny particles that eventually stabilize. This strengthens the aluminum matrix. This process can take anywhere from a few hours to a few weeks.
6061-T6
6061-T6 aluminum starts out the same as T4. However, instead of natural aging, you must apply artificial aging. You should heat it to ~160–180°C (320–356°F) for around 8 hours. By doing this, you lock the magnesium silicide (Mg₂Si) particles into place for maximum strength.
6061-T651
After heat treatment, quenching, and aging, there are some residual stresses in the T6 aluminum. To relieve those stresses, you must stretch it, usually by 1% to 3% strain. That way, you can machine it without too much distortion.
6061-T6511
The 6061-T6511 aluminum temper simply refers to T651 aluminum in extruded shapes, like bars and rods. You would use this temper to ensure extruded sections remain straight and meet tight tolerances.
6061 Aluminum: Properties
Now, let’s look at 6061 aluminum’s attributes. Generally speaking, it has good physical, mechanical, thermal, electrical, and chemical properties.
Physical
6061 aluminum is a lightweight alloy. It has a low density of approximately 2.70 g/cm³, or 2700 kg/m³. This equates to 0.0975 lb/in³.
When you look at it, it appears silvery-gray. You can make it matte or polished depending on the finish. You can also give it a smooth or textured surface. You’d do this by using various treatments and processes, like rolling, etching, or blasting.
6061 aluminum’s color and density remain the same across all tempers. However, its hardness changes depending on how you treat it.
| Temper | Approximate Brinell Hardness (HB) |
| 6061-O | 25-35 |
| 6061-T4 | 62-68 |
| 6061-T6/T651 | 95 |
Mechanical
Despite its light weight, aluminum is relatively strong. Again, it depends on which temper you’re working with.
| Property | 6061-O | 6061-T4 | 6061-T6 | 6061-T651 |
| Ultimate Tensile strength | 124 MPa (18,000 psi) | 241 MPa (35,000 psi) | 310 MPa (45,000 psi) | 310 MPa (45,000 psi) |
| Yield strength | 55 MPa (8,000 psi) | 145 MPa (21,000 psi) | 276 MPa (40,000 psi) | 276 MPa (40,000 psi) |
| Young’s modulus (E) | 68.9 GPa (10,000 ksi) | 68.9 GPa (10,000 ksi) | 68.9 GPa (10,000 ksi) | 68.9 GPa (10,000 ksi) |
| Elongation (ε) at break | ~18% | ~16% | ~8–10% | ~8–10% |
| Poisson’s ratio (v) | 0.33 | 0.33 | 0.33 | 0.33 |
As you can see, the strength increases with each level of temper while the elongation decreases. Elongation is a measure of formability. So, while 6061-O is extremely formable, it’s not particularly strong.
6061-T4 is stronger and still has good ductility. So, you may find it best to form components in this temper. Then afterwards, treat the aluminum again to reach the stiffest, strongest, T6 designation.
Thermal
The thermal conductivity of 6061 aluminum is fairly consistent, at approximately 151 to 202 W/mK. The linear thermal expansion coefficient also remains around ~23.6 µm//m-°C (13.1 µin/in-°F) across tempers.
The melting range of 6061 aluminum is from 582°C to 652°C (1080°F to 1205°F). The specific heat capacity is around 0.896 J/g-°C (0.214 BTU/lb-°F).
You’ll notice some differences in the thermal behavior between tempers, but nothing significant. The main takeaway is that 6061 aluminum has great thermal performance. This is why you can use it to fabricate parts for high-heat applications, like engine components and radiators.
However, when you increase the temperature, 6061 aluminum loses significant strength and hardness. You must factor this into your design calculations. It’s especially important if you’re fabricating parts that will be exposed to high temperatures. That means anything above 150°C (302°F) for prolonged periods.
Electrical
6061 aluminum is defined as having low electrical resistivity, typically around 0.038 μΩ/m. This makes it a moderately good conductor. It’s not as conductive as copper—it has around 40% of the International Annealed Copper Standard (IACS). But it is quite a lot lighter. So, if weight is an important factor for you, it works well.
Chemical
Aluminum (Al) is the base metal of the 6061 alloy. It accounts for between 95.85% and 98.56% of its chemical composition by mass. This is followed by magnesium (Mg), which makes up 0.80% to 1.20% of the alloy’s weight.
6061 aluminum must also contain silicon (Si) in concentrations from 0.40% to 0.80%. The copper (Cu) content must be between 0.15% and 0.40%. Chromium (Cr) can appear in levels from 0.04% to 0.35%.
Other elements may be present in 6061 aluminum in trace amounts. These include zinc (Zn) up to a maximum of 0.25% and titanium (Ti) up to 0.15%. Iron may appear in concentrations of up to 0.70%, and manganese (Mn) up to 0.15%.
Chemically speaking, one of 6061 aluminum’s main benefits is its resistance to corrosion. An oxide layer naturally forms on the material’s surface which creates a barrier layer. If you anodize 6061 aluminum, it will boost this protective effect.
Workability Characteristics
Machinability
The harder tempers of 6061 aluminum offer excellent CNC machinability. For example, you can easily mill, drill, cut, and tap T6 and T651 to tight tolerances.
However, softer tempers like 6061-O and T4 can gum up your cutting tools. In this case, you’ll need to adjust the tooling to account for the temper’s characteristics. For instance, this could include using higher rake angles.
In general, it’s recommended that you use carbide tools to machine 6061 aluminum. High-speed steel (HSS) won’t provide you wth sufficient strength.
Weldability
You can join all grades of 6061 aluminum using MIG, TIG, or resistance welding. However, the heat-affected zone (HAZ) can lose strength and is prone to cracking in harder tempers. So, you need to use the right filler material, like 4043 or 5356. You should also consider pre-heating and post-weld heat treatment to prevent cracking.
Heat Treatable
6061 aluminum alloy is precipitation-hardened. This is a heat-treatment technique. You can heat treat aluminum so well because of its chemical composition. The magnesium and silicone form precipitates (particles). When you heat it, they set in a certain way. This prevents movement or defects in the crystal structure.
Anodizing
You can apply clear and color anodizing (Type II) to 6061 aluminum. You can also use hard anodizing (Type III).If your priority is a uniform surface finish, T6 and T651 tend to be the best,
Common Applications Of 6061 Aluminum
6061 is extremely versatile. You can use it to create diverse parts and products. Here are the industries where you’d typically see it.
Automotive
If you work in the automotive industry, you’ll use 6061 aluminum alloy frequently. You can fabricate components in vehicle engines with it. You can also use it for vehicle chassis, suspensions, wheels, and body panels
Aerospace
When building an aircraft, you need parts that are as lightweight as possible. You also need them to reliably hold up to high stress. 6061 aluminum alloy is perfect for the job. You can use it for components in landing gear, wings, and fuselages.
Marine
6061 aluminum’s corrosion resistance makes it a top pick for various marine applications, like boat hulls, decks, and marine hardware.
Bike Frames
You can use 6061 aluminum to produce frames for mountain bikes, road bikes, electric bikes, and hybrid bikes.
Household Items
You’ll find 6061 aluminum in everything from cooking utensils to furniture frames and household appliances.
Construction
If you’re in construction parts manufacturing, you’ll work with 6061 aluminum regularly. You can use it for door handles, window frames, roofing, and other structural components.
Consumer Electronics
6061 aluminum is lightweight and conductive. This means you can use it for heat sinks and casings in electronic devices.
Custom CNC-Machined Parts
If you’re looking for a cost-effective material for industrial components, 6061 should be one of your top picks. You can machine it easily, so it’s great for custom parts.
Standard Forms
You can purchase 6061 aluminum in several forms, depending on what you intend to use it for. These are sheet, tube, bar, and plate. Each form has distinct advantages and limitations.
Sheet
A sheet of 6061 aluminum has a thin and flat geometry. This is achieved through rolling. You can typically buy it in thicknesses of 6 mm (0.25″) or less. It’s easy to bend, cut, and punch. You’ll see it used for signage, cladding, panels, siding, and enclosures.
Plate
Plate is essentially a thicker version of 6061 aluminum sheet. It’s defined by thicknesses greater than 6 mm (0.25″), produced by rolling or forging. Because of its extra thickness, it’s also more rigid and less formable. It’s ideal if you’re looking to fabricate jigs, molds, or tooling.
Tube
6061 aluminum tube has a structural hollow profile (SHS) and is usually cylindrical. However, it can also have a square, rectangular, or hexagonal profile. You can use it to create piping systems for transferring fluid like hydraulic oil or fuel. To create structural supports like scaffolding and framework, you would also use 6061 aluminum tube.
Bar
6061 aluminum bar refers to the solid extrudate. Much like aluminum tube, you can buy it with round, square, rectangular, or hexagonal cross-sections. It may also be flat. You can find 6061 aluminum bar in many diameters and widths. The most common range is from 0.25 to 16 inches. It’s a fantastic option if you intend to produce heavy-duty structural components using CNC machining and welding.
Material Standards/Compliance
When you manufacture 6061 aluminum, you’ve got to comply with various international and industry standards.
The American Society for Testing and Materials (ASTM) system determines the mechanical, chemical, and dimensional requirements. The specifications include:
- ASTM B209 for sheet and plate
- ASTM B210 for drawn seamless tubes
- ASTM B211 for bar, rod, and wire
- ASTM B221 for extruded bars, rods, wire, profiles, and tubes
- ASTM B241/B241M for seamless pipe and seamless extruded tube
In Europe, you’ll see the designation EN AW-6061 for 6061 aluminum. This is according to the European Norm (EN) system. These are the relevant standards:
- EN 485 for sheet, strip, and plate
- EN 573, relating to chemical composition and form
- EN 754 for cold-drawn rod, bar, and tube
- EN 755 for extruded rod, bar, and profile
The International Organization for Standardization also has standards that cover 6061 aluminum, like ISO 6361. Other industry-specific standards also exist. For example, Aerospace Material Standards (AMS).
Conclusion
If you need a strong, corrosion-resistant, lightweight material, 6061 aluminum is a brilliant choice. Whether you’re designing bike frames or engineering spacecraft, it gives you maximum durability and flexibility. Considering 6061 parts for your next project?
FAQ
How much does 6061 aluminum cost?
The price of aluminum varies depending on where you buy it from. Factors like form, quantity, and finish also influence the cost. As a general guide, a 1” thick plate of 12” x 12” may cost you between $180 to $220. Aluminum 6061 bars typically range from $2.00 to $12.50 per kg. You’ll get a lower price for ordering wholesale than buying retail.
What can you use 6061 aluminum for?
6061 aluminum has diverse applications. You can fabricate it into parts for shipbuilding, or use it to manufacture common household items. It’s ideal for structural components of aircraft, road vehicles, and buildings. You’ll also find Aluminum 6061 in electronic device components, like heat sinks.
Why is 6061 aluminum so popular?
The main reason 6061 aluminum is so popular is because of its versatility. It has a great strength-to-weight ratio and excellent corrosion-resistance. Plus, it’s incredibly easy to work with. You can weld it, machine it, and subject it to various other fabrication processes.
What’s the melting point of 6061 aluminum?
To melt 6061 aluminum, you’ll need to heat it to somewhere between 582°C and 652°C. The temperature ranges because of differences in the alloy’s composition. On the other hand, you can melt pure aluminum at 660.3°C because it doesn’t contain any other elements.
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