How Aluminum Alloy Grades Are Named
When you see a grade such as 6063-T5, the first four digits describe the chemical composition and the suffix describes the temper. The four-digit system is maintained by the Aluminum Association and adopted worldwide. The first digit names the principal alloying element: 1xxx is unalloyed aluminum (99.0% minimum), 2xxx adds copper, 3xxx manganese, 4xxx silicon, 5xxx magnesium, 6xxx magnesium plus silicon, and 7xxx zinc plus magnesium. The second digit records modifications to the original alloy, and the last two digits identify the specific alloy within the series. For 6063, the 63 identifies a particular Al-Mg-Si composition widely used for extruded architectural profiles.
What Does the T5 Temper Actually Do?
The T designation means the alloy has been thermally treated. For extrusions, T5 means the profile is cooled from the elevated-temperature shaping process (the extrusion press) and then artificially aged. In practice, the hot profile is quenched gently by air fans on the run-out table as it leaves the die, then loaded into aging ovens where it is held at about 175–185 degrees Celsius for several hours. This controlled aging precipitates the magnesium and silicon into fine strengthening phases inside the metal, raising hardness and yield strength while preserving a smooth, uniform surface that responds excellently to anodizing.
6063-T5 vs 6063-T6: Properties and Choice
| Property | 6063-T5 | 6063-T6 |
|---|---|---|
| Ultimate tensile strength | ≥150 MPa | ≥205 MPa |
| Yield strength | ≥110 MPa | ≥170 MPa (EN 755-2); ≥180 MPa (GB/T 5237.1) |
| Elongation A50 | ≥8% | ≥8% |
| Typical hardness | ≈8 Webster HW | Higher than T5 |
| Surface finish after anodizing | Excellent, uniform | Good |
Values shown are typical minimums quoted by ASTM B221, EN 755-2 and GB/T 5237 for standard 6063 profiles; exact figures depend on wall thickness and section design.
Which Temper Should You Choose?
T6 requires a solution heat treatment followed by rapid water quenching immediately after extrusion, which locks more alloying elements into solution and raises yield strength above 170 MPa. The trade-off is that water quenching makes thin-walled and complex sections more prone to distortion and slightly degrades the surface smoothness. T5, cooled by air and artificially aged, is the smarter choice for architectural framing, heat sinks, window and door systems, and any part with thin, intricate cavities where dimensional stability and surface quality matter more than maximum strength. For heavy structural load-bearing sections, T6 is the better specification.
Applications of 6063-T5 Profiles
Architectural framing: window frames, door frames, curtain walls and skylight structures, where corrosion resistance and finish are critical.
Industrial automation: machine guards, conveyor frames and T-slot framing systems valued for straightness and easy bolting.
Thermal management: extruded heat sinks with tall, thin fins that stay straight thanks to the gentle air-cooling process.
Furniture and displays: retail display racks, shower enclosures and lighting channels that take a bright, uniform anodized finish.
Buying Guide: Packaging, Certification and Sourcing
When buying extruded profiles factory-direct, protect your investment in transit: profiles separated by foam to prevent metal-on-metal scratching, wrapped in waterproof film against sea-moisture corrosion, and packed in fumigated wooden crates or on pallets for forklift handling. Always request a material test certificate confirming the temper and mechanical properties, and consider ordering standard lengths that maximize container utilization to reduce freight cost.
Frequently Asked Questions
Can a 6063-T5 profile be bent? Yes. Its lower yield strength compared with T6 makes it well suited to roll bending and rotary draw bending for arches and curved railings, with a reduced risk of cracking on the outer radius.
Does 6063-T5 rust outdoors? No. Aluminum contains no iron, so it cannot rust. It forms a thin, self-repairing oxide layer; for aggressive coastal environments, clear anodizing or powder coating adds decades of protection.
Can 6063-T5 be welded? Yes, with standard TIG or MIG methods. Note that welding heat destroys the T5 temper in the heat-affected zone, so local strength there will drop toward the annealed level.
What is the difference between 6061 and 6063-T5? 6061 is a structural alloy with higher strength, often used for load-bearing frames and marine parts. 6063 is the architectural alloy: easier to extrude into complex sections with a superior anodized finish, at a lower strength level.
What information do I need to provide for a 6063-T5 quotation? The exact grade and temper, a drawing or profile cross-section (DWG/DXF), surface treatment (mill finish, anodized or powder-coated), length per piece and total order quantity.
