Aluminum 6061 Vs 6063: Differences & How To Choose

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6063 and 6061 aluminum are 6xxx series alloys that contain silicon, magnesium, copper, and chromium. However, the difference between 6063 and 6061 aluminum comes down to composition. The balance of these elements causes them to behave quite differently in practice.

To learn more about aluminum 6061 vs 6063, this article covers the composition and the mechanical and physical properties of both aluminum alloys in detail. You’ll also find how each machines, resists corrosion, costs, and how to choose the right one.

What Is 6061 Aluminum?

6061 is a hard alloy that contains magnesium, silicon, copper, and chromium. It is commonly supplied in the T6 temper for higher strength and improved mechanical properties. The extra alloying content, particularly copper, gives it higher strength than most other 6xxx alloys.

Therefore, 6061 is ideal for high-strength applications such as trailers, truck beds, brackets, tooling plates, and aerospace parts. It is also one of the most popular aluminum alloys for CNC machining because it machines cleanly and holds tight tolerances.

What Is 6063 Aluminum?

6063 has the same alloying elements as 6061, but in smaller amounts. Copper is present in only trace amounts. This makes it easier to push through an extrusion die and form thinner walls than with 6061. It also anodizes more evenly, producing a cleaner, more consistent finish.

6063 is known as an architectural alloy used for window frames, railings, decorative trim, tubing, and retail display systems that require a smooth, high-quality finish.

Difference between 6063 and 6061 Aluminum

Both 6063 and 6061 alloys come from the same family, but the amount of each alloying element decides how each performs. Below is how they actually compare across composition, mechanical strength, physical properties, machinability, and real-world use.

Aluminum 6063 vs 6061: Quick Comparison

Property	6061 Aluminum	6063 Aluminum
Main Alloying Elements	Magnesium + Silicon	Magnesium + Silicon
Tensile Strength	Typically ~290 MPa (T6)	Typically ~240 MPa (T6)
Yield Strength	Typically ~240 MPa (T6)	Typically ~210 MPa (T6)
Machinability	Good	Good, but generally less suitable for demanding machining
Corrosion Resistance	Good	Excellent
Surface Finish	Good	Excellent, especially after anodizing
Extrudability	Good	Excellent
Weldability	Good	Good
Typical Applications	Machine parts, structural components, automotive parts	Extruded profiles, window frames, architectural and decorative parts
Best Choice When	Higher strength and structural performance are priorities	Surface appearance, extrusion, and corrosion resistance are more important

6061 vs 6063 Composition

6061 and 6063 are both 6xxx aluminum alloys with similar chemical compositions. However, 6061 contains more copper and chromium, contributing to its higher strength.

6061 and 6063 aluminum are both magnesium-silicon alloys, but their chemical compositions differ slightly. 6061 aluminum contains about 0.8–1.2% magnesium and 0.4–0.8% silicon, while 6063 contains lower amounts, with approximately 0.45–0.9% magnesium and 0.2–0.6% silicon.

6061 also contains more alloying elements that contribute to its higher strength. It typically contains 0.15–0.40% copper and 0.04–0.35% chromium, compared with a maximum of 0.10% for each element in 6063. Iron content is also limited to 0.70% maximum in 6061 and 0.35% maximum in 6063.

Overall, the higher levels of magnesium, silicon, copper, and chromium in 6061 provide better mechanical strength. Meanwhile, the leaner composition of 6063 makes it suitable for extrusion and applications that require a high-quality surface finish.

6061 vs 6063 Physical Properties

Physical properties describe how a material behaves in terms of its inherent characteristics, independent of applied force. These include density, melting point, and conductivity, whereby 6061 and 603 differ as shown below.

Physical Property	6061	6063
Density	2.70 g/cm³	2.70 g/cm³
Melting range	582 – 652°C	616 – 654°C
Thermal conductivity	154 W/m·K (T4) / 170 W/m·K (T6)	200 W/m·K
Electrical resistivity	3.99×10⁻⁶ ohm·cm (T6)	3.32×10⁻⁶ ohm·cm (T6)

Density is virtually identical at 2.70 g/cm³ for both alloys, which means alloy choice does not change part weight. However, 6063 conducts heat and electricity better than 6061, thanks to its lower copper and alloying content.

6061 vs 6063 Mechanical Properties

Mechanical properties describe how a material responds to applied forces. In 6061 and 6063 alloys, these properties vary depending on the temper condition, as shown in the table below.

Property	6061-T4	6061-T6	6063-T4	6063-T6
Tensile strength	241 MPa / 35,000 psi	310 MPa / 45,000 psi	172 MPa / 25,000 psi	241 MPa / 35,000 psi
Yield strength	145 MPa / 21,000 psi	276 MPa / 40,000 psi	90 MPa / 13,000 psi	214 MPa / 31,000 psi
Fatigue strength	96.5 MPa / 14,000 psi	97 MPa / 14,000 psi	68.9 MPa / 10,000 psi	68.9 MPa / 10,000 psi
Shear strength	165 MPa / 24,000 psi	207 MPa / 30,000 psi	110 MPa / 16,000 psi	152 MPa / 22,000 psi
Brinell hardness	65 HB	95 HB	46 HB	73 HB
Elongation at break	16%	12%	22%	15%
Modulus of elasticity	68.9 GPa / 10,000 ksi	68.9 GPa / 10,000 ksi	68.9 GPa / 10,000 ksi	68.9 GPa / 10,000 ksi

In general, 6061 aluminum is commonly used in the industry in the T6 temper, while 6063 aluminum is commonly used in the T5 temper.

6061-T6 (high strength): It has a tensile strength of up to 290–311 MPa and features high hardness, resistance to deformation and fatigue, and a strong load-bearing capacity. It is a safe and reliable choice for applications involving long-term stress, dynamic loads, and load-bearing structures.
6063-T5 (medium strength): With a tensile strength of only 160–180 MPa, it is significantly weaker, making it unsuitable for heavy loads. However, it has good ductility and resistance to brittle fracture, making it suitable for light-load and decorative structures.

Note: Do not use 6063 as a substitute for 6061 in load-bearing frames or supports. Although there may be no immediate problems, over time, it is highly likely to deform, sag, and crack, which can lead to serious safety hazards.

6061 Auminum vs 6063: Machinability and Fabrication

The machinability behavior of 6061 and 6063 aluminum differs due to their strength and hardness. Here’s how they compare in CNC machining, extrusion, forming, welding, and anodizing.

Process	6061	6063
CNC machining	Excellent with short, brittle chips, clean cuts, and tight tolerances	Fair. Produces long, stringy chips because it is softer and more gummy
Extrusion	Good, but limited to simpler profiles	Excellent and ideal for thin-wall, intricate shapes
Bending and forming	Good, but less ductile than 6063 in T6	Easier to bend without cracking, especially in T4 or T52
Welding	Good, but HAZ drops to 40–50% of base strength	Good with proportional HAZ drop, but less problematic at lower base strength
Anodizing	Possible, but the finish can be dull or slightly tinted	Excellent, producing a clear, even, consistent anodized surface

Aluminium alloy 6063 is soft and has good fluidity. It offers low extrusion resistance, making it easy to extrude thin-walled, irregularly shaped and complex-section profiles. It enables fast extrusion speeds, high yield rates and low production costs. It accounts for over 90% of doors, windows, curtain walls, irregular frames and lightweight profiles on the market.

In contrast, 6061 aluminium has high extrusion resistance and moderate ductility, making it suitable only for simple cross-sections, thick-walled profiles, aluminium sheets, rods and blocks. Nevertheless, when it comes to CNC machinability, this product is second to none. It delivers stable cutting performance and high dimensional accuracy, making it the go-to choice for those seeking precision industrial parts.

How to Choose Between 6063 and 6061

The choice between these two types of aluminum depends on the functional requirements of the application.

Aluminum 6061 vs 6063 Applications

Applications of 6061 Aluminum

6061 aluminum is widely used for industrial structures, mechanical components, and load-bearing parts because of its higher strength and good machinability. Typical applications include:

Automation equipment frames, fixtures, and machine bases
CNC-machined precision parts, mechanical components, and mold plates
Automotive components, support brackets, and machinery structures
Aluminum parts requiring good wear resistance or hard anodizing
Aluminum plates, bars, and thick-wall tubes used for industrial components

Applications of 6063 Aluminum

6063 aluminum is particularly suitable for extruded profiles, architectural applications, and lightweight structures. Its excellent extrudability and surface finish make it a common choice for:

Doors, windows, curtain walls, and railings
Furniture frames, decorative trims, and kitchen or bathroom profiles
Heat sinks, thin-wall profiles, and decorative components
Lightweight production-line frames and non-load-bearing structures

Quick Decision Tips

Choose 6061:

Load-bearing, structural, or long-term stress
CNC precision parts or mechanical components
Thick plates, bars, or tubes
Hard anodizing or higher wear resistance

Choose 6063:

Decorative or exposed parts
Doors, windows, curtain walls, or railings
Complex or thin-wall extruded profiles
Smooth surface and uniform anodizing

In short: Choose 6061 for strength; choose 6063 for appearance and extrusion performance.

How to Tell 6061 from 6063 Aluminum

6063 and 6061 alloys look almost identical, which makes it hard to tell them apart by eye. However, you can identify them using the following methods.

Mill markings and certificates: Stock is typically stamped, tagged, or shipped with a mill certificate stating alloy and temper. This is the only fully reliable identification method for compliance purposes.
Chip test: A light machining pass tells the difference, whereby 6061 produces short, brittle chips while 6063 produces long, gummy, stringy ones.
Anodizing test: When 6063 is anodized, it comes out clear and uniform. In contrast, anodizing 6061 often finishes duller or with a slight tint due to its higher iron and copper content.
XRF testing: A handheld X-ray fluorescence (XRF) analyzer helps identify an alloy by measuring its chemical composition, making it easy to distinguish 6061 from 6063.

Conclusion

Both 6061 and 6063 aluminium have their own advantages. 6061 is the better choice for strength, structural performance and CNC-machined components, whereas 6063 is better suited to extrusion and decorative applications, as well as parts that require an excellent surface finish. Selecting the appropriate alloy for your application can help ensure reliable part performance and avoid unnecessary manufacturing costs.

Need custom aluminium parts?

At FS Fab, we provide CNC machining for 6061, 6063 and other aluminium alloys. Our capabilities include multi-axis CNC machining, surface finishing and quality inspection. Send us your drawings or specifications to discuss the most suitable material and manufacturing solution for your project.

FAQs

Can you weld 6061 to 6063 aluminum?

They weld well together using a 4xxx or 5xxx filler rod. However, expect some strength loss in the heat-affected zone, primarily on the 6061 side. HAZ strength can drop significantly there.

Can 6063 be used instead of 6061 for a structural part?

6063-T6 is weaker than 6061-T6, so using 6063-T6 for structural parts can result in a lower yield strength. However, if the application is lightly loaded, replacing 6063 with 6061 may be acceptable, though verification is required.

Which aluminum extrusion alloy should I choose: 6061 or 6063?

Choose 6063 if your extrusion requires thin walls, intricate profiles, a smooth anodized finish, or an architectural appearance. However, choose 6061 if the extrusion must carry a structural load, maintain tight tolerances, or perform under fatigue loading.

Is 6061 more expensive than 6063?

6061 alloy costs more than 6063 in comparable mill forms. This is because of the higher alloying content and tighter quality control around copper and chromium additions. Also, the cost difference is influenced by the LME aluminum rates, product form (sheet, plate, extrusion, bar), and order volume.

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About the Author

Stephen Musau

Stephen is a content writer and editor with a strong background in Mining and Mineral Processing Engineering. He enjoys helping readers understand CNC machining, materials, and industrial processes in a clear and practical way. Stephen focuses on creating content that is accurate, well-researched, and easy to follow, making complex technical topics accessible to everyone.