Key takeaways
- 6061-T6 is roughly 30% stronger than 6063-T6 and well over 50% stronger than 6063-T5.
- 6063 extrudes faster into thinner, more complex shapes, which usually makes it cheaper.
- 6063 anodizes to a brighter, more uniform finish; 6061 looks slightly greyer.
- 6063 conducts heat better (≈ 200 vs ≈ 167 W/m·K) — the reason heat sinks use it.
- For structural profiles with thin walls, 6005A is often the better middle ground.
6061 and 6063 are the two best-known aluminum extrusion alloys. Both belong to the heat-treatable 6000 series, strengthened by magnesium and silicon, and both are easy to weld and resist corrosion well. The differences come from composition: 6061 carries more magnesium and silicon plus copper and chromium, which makes it stronger but harder to push through a die.
Side-by-side comparison
| Property | 6063 | 6061 |
|---|---|---|
| Main alloying (wt %) | Mg 0.45–0.9, Si 0.2–0.6 | Mg 0.8–1.2, Si 0.4–0.8, Cu 0.15–0.4 |
| Tensile strength, T6 | ≈ 215–245 MPa | ≈ 260–310 MPa |
| Yield strength, T6 | ≈ 170–215 MPa | ≈ 240–276 MPa |
| Tensile strength, T5 | ≈ 175–190 MPa | — (usually supplied T6) |
| Thermal conductivity | ≈ 200–209 W/m·K | ≈ 167 W/m·K |
| Extrudability | Excellent | Fair |
| Anodized appearance | Excellent, bright and uniform | Good, slightly greyer |
| Machinability | Fair (gummy chips) | Good |
| Weldability | Good | Good |
| Relative profile cost | Lower | Higher |
Indicative ranges; guaranteed minimums depend on wall thickness and standard. Check the mill certificate.
When to choose 6063
- Architectural profiles — windows, doors, curtain wall, railings.
- Visible products — anything anodized or brushed where appearance sells.
- Thermal parts — heat sinks, LED channels and enclosures that dissipate heat.
- Complex or thin-walled sections — multi-hollow shapes, fine fins, snap-fits.
- T-slot framing and furniture — where stiffness, not ultimate strength, governs.
When to choose 6061
- Load-bearing structures — brackets, frames and members sized by strength.
- Heavily machined parts — 6061 breaks chips cleanly and holds threads better.
- Fatigue-critical parts — bicycle frames, fixtures under cyclic load.
- Simple, robust sections — where the harder extrusion does not add much cost.
The middle ground: 6005A and 6082
If you need more strength than 6063 but have a thin-walled or hollow section, 6005A is often the best answer: near-6061 strength with much better extrudability. 6082 is Europe’s standard high-strength structural alloy and a common alternative to 6061.
A simple decision rule
- Start with 6063.
- If stress calculations show it is not strong enough, try 6063-T6 or T66 before changing alloy.
- If you still need more, move to 6005A for thin-walled or hollow sections, or 6061/6082 for solid, robust sections and heavy machining.
Not sure? Send your drawing and loads with your RFQ and our engineers will recommend an alloy and temper.
Frequently asked questions
Is 6061 or 6063 better for outdoor use?
Both have good corrosion resistance. 6063 is preferred for visible architectural parts because of its superior anodized finish; 6061 is used outdoors where strength matters more than appearance.
Can you weld 6061 and 6063 together?
Yes. They are commonly welded with 4043 or 5356 filler wire. As with any 6000-series alloy, the heat-affected zone loses strength unless the assembly is heat-treated again.
Why is 6063 cheaper to extrude than 6061?
6063 flows through dies at higher speed and lower pressure, and allows thinner walls and more complex dies, so press time per kilogram is lower.