Because of its tremendous versatility, aluminum is the raw material of choice for numerous applications in a variety of industries. One of the applications that is especially well suited for aluminum is extrusion. Both 6061 and 6063 aluminum alloys are popular choices for these applications, and because of their similarities, it can sometimes be difficult for manufacturers to choose between them.
What Exactly Is Extrusion?
Extrusion is a process that transforms a material, such as rubber, plastic, or metal, into particular shapes and objects. Aluminum is especially popular for extrusion because of the metal’s physical characteristics. Aluminum alloys offer both malleability and formability that means they can be easily machined and cast, but they are as much as one-third the density of steel. This results in extrusions that are both strong and stable, at a reduced cost relative to other materials. This is why aluminum is the most common metal used in extrusion.
The aluminum extrusion process begins with designing and creating the die that will shape the raw material. Once this has been done, a cylindrical billet of aluminum is heated up in a forge to high temperatures, generally between 800°F-925°F. Next, a lubricant is added to the aluminum to prevent it from sticking to any of the machinery. It is then placed on the loader and pressure is applied with a ram that propels the aluminum through the die.
During this process, nitrogen is added in order to prevent oxidation. The extruded part will pass completely through the die and out the other side. It has now been elongated in the shape of the die opening. The finished extrusion is then cooled, and if necessary, a process of straightening and hardening creates the finished product. They can be cut to the desired lengths and undergo a final aging process before being ready for market. There are also numerous options for transforming the color, texture, or finish, as well as anodizing or painting the extrusion.
Which Alloys Can Be Used In Extrusion?
Aluminum is known for the diversity of its alloys, but not all of them are suitable for extrusion. Generally, three classes of aluminum alloys are used in extrusion, the 1000 series, 6000 series, and 7000 series. Because the 1000 series is not heat treatable, they are often used in products where high thermal and electrical conductivity are the desired properties. However, the 1000 series alloys offer low strength.
Both 6000 and 7000 series alloys are heat treatable. For the 7000 series, these alloys offer excellent weldability and greater strength in the parts of the material that have been heat affected than the 6000 series. The drawback is that they do not have the same level of corrosion resistance and formability as the 6000 series.
The 6000 series is well recognized for its excellent extrudability. In addition, these alloys can be heat treated at the extrusion temperature, making them strong, easily weldable, and corrosion resistant in the harshest environments. That’s why this series is extremely popular for extrusion applications in a number of industries, in particular construction.
How To Choose Between 6061 And 6063 Alloys?
Two of the most common alloys for extrusion are 6061 and 6063. Although they possess many of the same qualities, they each offer their own distinct properties that mean manufacturers need to do their research when deciding between them.
The second most popular aluminum for extrusion, 6061 is precipitation-hardened and uses magnesium and silicon as its major alloying elements. It was first developed in 1935 as part of the early advances in the aircraft industry. It offers good weldability and machinability, good joining characteristics, accepts applied coatings well, and is highly corrosion resistance while having a high strength to weight ratio.
In contrast, 6063 is the most popular aluminum used for extrusion. It also uses magnesium and silicon as its alloying elements. Its unique properties allow it to be formed into complex shapes with very smooth surfaces, making it fit for anodizing. Its major drawback compared to 6061 is that it does not have the same level of strength.
In comparing the specific properties of the two alloys, 6061 has a density of 2.7 g/cm cubed. The Young’s modulus is rated at 68.9 GPa with a tensile strength of 124-290 MPa. The elongation at break is 12-25%. It has a melting temperature of 585 degrees Celsius, thermal conductivity of 151-202 W/(m·K), and a specific heat capacity of 897 J/ (kg·K). The linear thermal expansion coefficient is 2.32 x 10−5 K−1. Finally, the volume resistivity is 32.5–39.2 nOhm·m.
By contrast, 6063 offers a density of 2.69g/ cm3. It’s Young’s modulus is 68.3 GPa and it has a tensile strength of 145–186 MPa. It has a slightly higher elongation at break at 18-33%. 6063 offers a melting temperature of 615 °C, thermal conductivity of 201-218 W/(m·K), and a specific heat capacity of 900 J/ (kg·K). The linear thermal expansion coefficient is 2.34 x 10−5 K−1, and the volume resistivity is 30-35 nOhm·m.
Of course, knowing the listed specifications is not the same thing as seeing how an alloy actually responds to your particular application. Manufacturers need to take the time to test an alloy to ensure it performs as desired with their production processes. Aluminum, because of its formability and versatility, is especially useful for this kind of prototyping.
What Are The Common Applications For 6061 And 6063 Alloys?
6061 aluminum alloy is found in a wide variety of applications. It is used in bicycle frames and components, fly fishing reels, firearm sound suppressors and other weapon parts, aluminum docks and gangways, ultra-high vacuum chambers, remote-controlled aircraft, and other toys and models. In extruded form, it is very common in construction applications that require higher strength than 6063 is able to offer.
6063 is commonly used in visible architectural applications such as window frames, door frames, roofs, and sign frames where high strength is not the most important factor. It is also popular in pipe and tubing, as well as aluminum furniture.
Summary
No matter what your particular application, you need an aluminum supplier who can be your partner in the production process. At Clinton Aluminum, we take pride in working with our customers to be their technical resource partner, and we will do our best to help you select the right material for your production needs.
