6061 vs 6063 Aluminum
6061 and 6063 are both Mg-Si extrusion alloys, but 6061 carries more silicon, magnesium and a little copper and chromium, so it heat treats to about 276 MPa yield in T6 against roughly 215 MPa for 6063-T6 and 145 MPa for the common 6063-T5. 6063 pays for that with a better extruded surface, thinner walls and sharper corners, and a clearer, more uniform anodized finish.
The split is structural versus architectural. Frames, machine bases, brackets and anything with a load calculation get 6061, which is also stocked as plate, bar and tube. Window and door frames, trim, heat sink fins, light poles and cosmetic extrusions get 6063.
| Property | 6061-T6 | 6063-T5/T6 |
|---|---|---|
| Alloy family | 6xxx (Mg-Si) with Cu, Cr | 6xxx (Mg-Si), leaner |
| Tensile | 310 MPa (45 ksi), T6 | 186 MPa (27 ksi) T5; 241 MPa (35 ksi) T6 |
| Yield | 276 MPa (40 ksi), T6 | 145 MPa (21 ksi) T5; 215 MPa (31 ksi) T6 |
| Elongation | 12-17%, T6 | 8-12% |
| Density | 2.70 g/cm³ | 2.70 g/cm³ |
| Hardness | ~95 HB | ~60 HB T5; ~73 HB T6 |
| Extruded surface | Good | Excellent; thinner walls, tighter corners |
| Anodized appearance | Good; slight yellow tint possible | Excellent; clear and uniform |
| Thermal conductivity | ~167 W/m·K | ~200 W/m·K |
| Product forms | Plate, bar, tube, extrusions | Extrusions, some tube |
| Typical uses | Structural frames, machined parts, T-slot | Architectural trim, window frames, heat sinks, railings |
Typical values for the stated conditions. Confirm against the mill certificate and your spec.
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Decision matrix
A check marks the side with the edge on that dimension.
| Dimension | 6061-T6 | 6063-T5/T6 |
|---|---|---|
| Machining | ✓ Good; T6 chips well | Fair; softer, gummier, more burr |
| Welding | Good; HAZ loses T6 | Good; same fillers, HAZ softens |
| Forming | Fair in T6 | ✓ Good; T5 bends more easily |
| Strength | ✓ 276 MPa yield T6 | 145-215 MPa yield |
| Corrosion resistance | Good | ✓ Slightly better; less copper |
| Finishing | Anodizes well; color less uniform | ✓ Anodizes beautifully; the architectural standard |
| Material cost | Baseline | Similar per pound; complex profiles cheaper to extrude |
| Availability | ✓ All forms everywhere | Extrusions everywhere; little plate or bar |
Choose 6061-T6 when
- Structural frames, machine bases and anything sized by a stress calculation
- Machined parts from plate, bar or tube
- Extrusions that will be tapped, bolted or loaded heavily
- Higher hardness for wear or thread strength
Choose 6063-T5/T6 when
- Architectural and cosmetic extrusions with a clear anodized finish
- Thin-wall, complex or hollow profiles that 6061 will not extrude cleanly
- Heat sinks, where the better conductivity and fin geometry matter
- Railings, window and door frames, trim and light-duty structure
Frequently asked questions
- Is 6061 stronger than 6063?
- Yes. 6061-T6 yields at about 276 MPa; 6063-T6 at about 215 MPa and the common 6063-T5 at about 145 MPa. For a loaded part, 6061 in T6 is the default unless the profile can only be extruded in 6063.
- Which anodizes better?
- 6063. Its lower alloy content gives a clear, uniform anodized layer with consistent color across a batch, which is why architectural and consumer extrusions are 6063. 6061 anodizes well but can show a faint yellow or gray tint and more variation.
- What is the difference between 6063-T5 and T6?
- T5 is cooled from the extrusion press and artificially aged with no separate solution treatment; T6 is solution heat treated, quenched and aged. T6 is stronger (about 215 vs 145 MPa yield) but costs more and is less common in architectural stock.
- Can I get 6063 in plate or bar?
- Rarely. 6063 is an extrusion alloy and is stocked as profiles, tube and some rod. Plate and bar are 6061. If a design needs both a cosmetic extrusion and machined plate parts, expect to use both alloys.
