Why Alloy Selection Matters
Selecting the right aluminum alloy is one of the most consequential decisions in any extrusion project. The alloy you choose determines the mechanical strength of the finished profile, its corrosion resistance, how well it responds to surface finishing, how complex a cross-section the die can produce, and ultimately the cost of the final part. An alloy that is overspecified for the application adds unnecessary material cost and may introduce manufacturing difficulties. An alloy that is underspecified can lead to premature failure, warranty claims, and costly redesigns.
The aluminum alloy numbering system groups alloys by their primary alloying elements. For extrusion, the 6xxx series (aluminum-magnesium-silicon) dominates, accounting for over 80% of all extruded profiles worldwide. These alloys offer an excellent balance of extrudability, strength, corrosion resistance, and finishing response. Within the 6xxx family, however, significant differences exist. The 7xxx series (aluminum-zinc-magnesium) serves specialized high-strength applications where the performance requirements justify higher material and processing costs.
In this guide, we examine four alloys that represent the practical range of options for most extrusion projects: 6063, 6061, 6082, and 7075. Understanding their differences will help you make an informed selection that optimizes performance, manufacturability, and cost.
6063: The Architectural Standard
Alloy 6063 is the most widely extruded aluminum alloy in the world, and for good reason. Its chemical composition — approximately 0.4% silicon and 0.7% magnesium — gives it outstanding extrudability, meaning it flows smoothly through the die at relatively low pressures. This allows for the production of complex, thin-walled profiles with tight dimensional tolerances and excellent surface quality directly off the press.
In the T6 temper condition (solution heat treated and artificially aged), 6063 achieves a typical ultimate tensile strength of approximately 215 MPa and a yield strength of around 170 MPa. While these values are moderate compared to higher-strength alloys, they are more than adequate for the vast majority of architectural, decorative, and general-purpose applications. The alloy offers excellent corrosion resistance in atmospheric and marine environments without the need for protective coatings, though it responds beautifully to both anodizing and powder coating when aesthetic or additional protective requirements exist.
Common applications for 6063 include window and door frames, curtain wall mullions, railing systems, display fixtures, furniture components, and heat sink profiles. Its superior surface finish after anodizing makes it the default choice for any application where visual appearance is a primary concern. The T5 temper (air quenched and artificially aged) is also widely used where slightly lower mechanical properties are acceptable, offering cost savings through simplified heat treatment.
If your application prioritizes surface quality, complex profile geometry, and corrosion resistance over high structural strength, 6063 should be your starting point.
6061: The Structural Workhorse
When an application demands higher mechanical strength while retaining good all-around properties, 6061 is typically the next alloy to consider. With a composition containing approximately 1.0% magnesium, 0.6% silicon, 0.3% copper, and 0.2% chromium, 6061 delivers significantly higher strength than 6063. In the T6 temper, 6061 achieves an ultimate tensile strength of approximately 310 MPa and a yield strength of around 275 MPa — roughly 45% stronger than 6063-T6.
The addition of copper and chromium to the alloy enhances strength and toughness but comes with trade-offs. Extrudability is reduced compared to 6063, meaning that profile geometry must be somewhat less complex, minimum wall thicknesses are slightly higher, and extrusion speeds are lower. Surface finish after anodizing, while still good, does not achieve the same level of visual uniformity as 6063. The copper content also marginally reduces corrosion resistance, although 6061 still performs well in most atmospheric environments.
What makes 6061 particularly versatile is its excellent weldability. It can be reliably welded using TIG and MIG processes with 4043 or 5356 filler alloys, making it a preferred choice for fabricated structural assemblies. It also machines well, producing clean chips and good surface finishes in CNC operations.
Typical applications include structural framing, machine bases, automotive chassis components, marine fittings, bicycle frames, and any load-bearing application where the profile must withstand significant mechanical stress. If your project involves structural loads, welded assemblies, or extensive machining, 6061 is the alloy to evaluate first.
6082: High-Strength Alternative
Alloy 6082 occupies a similar strength class to 6061 but with a different balance of properties that makes it the preferred structural alloy in European and many international markets. With approximately 0.9% silicon, 0.7% magnesium, and 0.5% manganese (replacing the copper found in 6061), 6082-T6 achieves an ultimate tensile strength of approximately 310 MPa and a yield strength of around 260 MPa.
The key advantage of 6082 over 6061 lies in its corrosion resistance. By replacing copper with manganese as a strengthening element, 6082 avoids the slight reduction in corrosion performance that copper introduces. This makes it particularly well-suited for outdoor structural applications, marine environments, and infrastructure projects where long-term durability without protective coatings is essential. The manganese content also refines the grain structure, contributing to improved toughness and fatigue resistance.
Extrudability of 6082 is comparable to 6061, meaning it is somewhat more challenging to extrude than 6063 but readily achievable for standard structural profiles. The alloy welds well and machines cleanly, making it a direct substitute for 6061 in most applications. It is widely specified for bridge structures, crane components, offshore platforms, transport vehicle frames, and scaffolding systems.
If your application requires 6061-class strength with improved corrosion resistance, or if your project must comply with European structural standards (Eurocode 9), 6082 is the logical choice.
7075: Aerospace-Grade Performance
At the top of the strength spectrum sits 7075, an aluminum-zinc-magnesium-copper alloy originally developed for aircraft structural applications. In the T6 temper, 7075 achieves an ultimate tensile strength of approximately 570 MPa and a yield strength of around 505 MPa — making it nearly three times stronger than 6063-T6 and approaching the strength of many structural steels at roughly one-third the weight.
This exceptional strength comes at a cost. 7075 is significantly more difficult to extrude than 6xxx series alloys. Its high flow stress requires greater press force, limiting achievable profile complexity and production speed. Minimum wall thicknesses are substantially higher, and dimensional tolerances are wider than what can be achieved with 6063 or 6061. The alloy has limited weldability using conventional fusion processes, and its corrosion resistance is notably lower than the 6xxx alloys, typically requiring protective surface treatments such as anodizing or primer/paint systems for applications exposed to moisture.
Material cost for 7075 billet is significantly higher than 6xxx alloys, and the reduced extrusion productivity further increases the per-kilogram cost of finished profiles. For these reasons, 7075 is specified only when the strength-to-weight ratio is the overriding design criterion and no 6xxx alloy can meet the structural requirements.
Typical applications include aerospace structural members, high-performance sporting goods (such as competitive bicycle and climbing equipment), defense components, and precision-machined parts where maximum strength at minimum weight is essential. If your application can meet its performance targets with a 6xxx alloy, that will almost always be the more practical and cost-effective path.
Making Your Selection
Choosing the right alloy begins with a clear understanding of what your application actually requires. Consider these key factors in order of priority for your specific project:
Mechanical loads: What tensile, compressive, and bending forces will the profile experience in service? If loads are moderate and the application is non-structural, 6063 will likely suffice. If the profile is load-bearing, 6061 or 6082 should be evaluated. Reserve 7075 for cases where the structural analysis demonstrates that no 6xxx alloy can meet the safety factors required.
Profile complexity: Highly complex cross-sections with thin walls, tight radii, and hollow chambers are most achievable in 6063. As you move to 6061, 6082, and especially 7075, profile geometry must be progressively simplified. Discuss your profile design with our engineering team early to ensure it is compatible with your target alloy.
Surface finish requirements: If the profile will be anodized for decorative purposes or will be visible to the end user, 6063 delivers the best aesthetic result. For powder-coated or painted applications, all four alloys perform well since the coating covers the substrate surface.
Corrosion environment: For uncoated profiles in corrosive environments, 6063 and 6082 offer the best natural corrosion resistance. 6061 performs adequately in most atmospheric conditions but may require protective treatment in marine or chemical environments. 7075 typically requires surface protection in any corrosive exposure.
Post-extrusion fabrication: If the profile will be welded, 6061 and 6082 are the strongest choices with established welding procedures. If extensive CNC machining is planned, all four alloys machine well, though 6061 and 7075 produce particularly clean finishes in machined surfaces.
For a comprehensive comparison of all alloy grades we offer, including detailed mechanical property data and processing guidelines, visit our Alloy Guide. You can also explore our full Alloys page for specifications on every grade in our production range. If you are uncertain which alloy is right for your project, our metallurgical and extrusion engineering team is available to review your application requirements and recommend the optimal grade. Contact us to start the conversation.