Among the numerous aluminum alloy grades, 6061 and 6063 are often the two primary options engineers and designers face when selecting materials. Both belong to the heat-treatable 6XXX series of aluminum alloys, renowned for their excellent corrosion resistance and good weldability. However, despite both containing magnesium and silicon as primary alloying elements, their slight differences in chemical composition result in distinctly different mechanical properties and processing characteristics, thereby determining their suitability for different application areas. Under what circumstances should one choose the stronger, more versatile 6061, or the easier-to-extrude 6063 with its excellent surface finish? We will delve into the chemical composition, properties, and typical applications of these two alloys to help you make an informed material selection.
Aluminum 6061
6061 aluminum, known as “structural aluminum,” is a widely used alloy. It belongs to the 6000 series of aluminum alloys, which utilize magnesium and silicon to enhance strength and lower the melting point. This alloy exhibits excellent corrosion resistance, weldability, and tensile strength. Heat treatment can further enhance its strength through artificial aging. Its outstanding machinability and formability make it the preferred choice for extruded products.
Compared to specialized aluminum alloys, 6061 is versatile and cost-effective. While its physical properties are not exceptional, its versatility and ease of machining in metal forming processes remain unmatched.
Application Areas:
Transportation: Aircraft structures, automotive components, railway tank cars, ship hull structures, etc.
Building Structures: Heavy-duty structures, bridge components, etc.
Sports equipment: Bicycle frames, baseball bats, hockey sticks, etc.
Electronics: Smartphone cases, laptop cases, etc.
Other: Pipes, photography equipment accessories, military gear, etc.
Aluminum 6063
6063 aluminum, commonly referred to as “building aluminum,” is specifically designed for ease of extrusion and has a surface that is easily anodized. 66063 It has excellent corrosion resistance, especially after proper surface treatment. It is known for its good weldability, solderability, and machinability, as well as moderate tensile strength and good machinability. 6063 is widely used in extrusion applications and is highly favored in the construction, entertainment, and furniture industries, particularly in environments where exposure to weather or water is expected.
Application Areas:
Construction Industry: Window frames, door frames, curtain walls, architectural decorative profiles, railings, etc.
Furniture: Various furniture frames, tubing, etc.
Home Appliances: Radiators, appliance housings, etc.
Store Accessories: Display racks, shelves, etc.
Other: Irrigation pipes, lighting equipment, etc.
Chemical Composition of Aluminum 6061 vs 6063
| Alloy | Mn | Fe | Mg | Si | Cu | Zn | Ti | Cr | Other (Each) | Others (Total) | Al |
| 6061 | 0.0 – 0.15% | 0.0 – 0.70% | 0.80 – 1.20% | 0.40 – 0.80% | 0.15 – 0.40% | 0.0 – 0.25% | 0.0 – 0.15% | 0.04 – 0.35% | 0.0 – 0.05% | 0.0 – 0.15% | Balance |
| 6063 | 0.0 – 0.10% | 0.0 – 0.35% | 0.45 – 0.90% | 0.20 – 0.60% | 0.0 – 0.10% | 0.0 – 0.10% | 0.0 – 0.10% | 0.0 – 0.10% | 0.0 – 0.05% | 0.0 – 0.15% | Balance |
Copper (Cu) content: 6061 contains a higher proportion of copper, which gives it superior strength and hardness but also slightly reduces its corrosion resistance (compared to 6063).
Silicon (Si) and magnesium (Mg) content: Although both contain silicon and magnesium, 6061 typically has a higher proportion of silicon and magnesium, further enhancing its strength. 6063 has relatively lower silicon and magnesium content, which gives it better extrusion performance and surface treatment properties.
Impurity elements: 6063 has stricter requirements for impurity elements such as iron, which helps improve its surface finish and anodizing results.
Weldability of Aluminum 6061 vs 6063
6061 aluminum alloy has excellent weldability and can be welded using the most common welding processes, such as TIG welding and MIG welding. Aluminum alloy welded joints can also withstand significant loads. 6063 aluminum alloy also has good weldability.
Machinability of Aluminum 6061 vs 6063
6063 aluminum alloy has excellent extrusion properties, good fluidity, and can be extruded into complex cross-sectional shapes. It is relatively soft, requiring less force and speed during cutting. Additionally, it has a high surface finish, making it ideal for producing various profiles, such as door and window frames, decorative strips, etc.
6061 aluminum alloy also has good machinability and can be welded and machined, but its extrusion performance is inferior to 6063. It is more suitable for manufacturing components requiring higher strength, such as mechanical parts and brackets. Machining 6061 produces sticky chips, and it is more difficult to machine than 6063. These chips are shorter and require lubrication for even the simplest cutting operations.
Heat Treatment of Aluminum 6061 vs 6063
The heat treatment for 6061 and 6063 is slightly different, resulting in different properties. 6061 and 6063 are typically in T4 and T6 conditions, respectively, after natural aging and artificial aging. The T6063 condition for 6063 involves three steps: solution heat treatment at 510°C, quenching at 175-190°C, and aging for 5-8 hours. 6061-T6 also undergoes three steps: solution treatment at 527°C, quenching, and artificial aging at 10-20°C for 160-180 hours. After artificial aging, both alloys exhibit reduced formability and ductility, while strength and corrosion resistance are enhanced. 6061 has a lower melting temperature and thermal conductivity, which is why its T6 temperature is slightly higher than that of 6063.
To eliminate artificial aging or mitigate the T6 effect to achieve optimal strength and toughness, 6061 and 6063 are annealed at 413°C for 2–3 hours (cooling rate of 10°C/hour) and at 415°C for 2 hours, respectively. The temperature and holding time can be adjusted based on the performance requirements of the specific application.
Which is better, 6061 or 6063?
Compared to 6063, 6061 forms smooth surfaces with complex shapes. Both 6061 and 6063 are structural materials used in furniture, recreational components, truck bodies, and window frames. Aircraft components, automotive bodies, fillers, hydraulic pistons, and brake structures are all manufactured using 6061 aluminum alloy. Additionally, compared to 6063, 6061 is suitable for ladders and bridge components due to its high strength and resistance to deformation.
As mentioned earlier, 6061 has excellent electrical conductivity, making it suitable for couplings, electrical fillers, and connectors. Its good corrosion resistance makes it an excellent choice for beverage cans.
Furthermore, 6063 can be used in general building products such as window frames, stair railings, and roofs, as it is easy to anodize and has good aesthetic appeal. Pipes, decorative components, structural supports, brackets, and conduits are also some applications of 6063. Due to its oxidation resistance, high corrosion resistance, and durability, household aluminum products such as cans can be recycled into more cans.
If thermal or electrical conductivity is critical in an application, aluminum alloys are a better choice than steel, and due to this property, they are used in power transmission lines. 6061 has better electrical conductivity than 6063.
Conclusion
Selecting the appropriate aluminum alloy (whether 6061 or 6063) depends on the specific requirements of your application. Both alloys can be formed using various aluminum forming techniques to achieve satisfactory product performance. The details of your project will play a key role in determining which alloy is more suitable for your intended application.
Aluminum 6061 is the second most popular aluminum alloy for extrusion, with a slightly higher strength-to-weight ratio compared to 6063. It offers excellent machinability and weldability, making it a versatile alloy suitable for a wide range of applications. If strength is a priority over corrosion resistance, opt for 6061.
On the other hand, 6063 alloy is the most popular aluminum alloy for extrusion. Notably, it offers slightly superior corrosion resistance and an aesthetically pleasing surface finish, making it ideal for anodizing. It is the preferred choice for applications requiring sufficient strength and enhanced corrosion resistance.