Aluminum Round Bar & Square Bar Buying Guide: 6061 vs 6063 vs 7075 — How to Specify Aluminum Bar by Alloy and Temper
Aluminum bar — round and square sections for machining, welding, and structural fabrication — is bought by alloy and temper, and the pair decides nearly everything. 6061-T6 machines beautifully and is the default; 6063 extrudes well but machines poorly; 7075 is the hardest and most expensive. Order 7075 where 6061 would do and the machining cost alone doubles your part price.
This guide compares the main alloys, tempers, surface conditions, and a complete RFQ checklist.
6061 vs 6063 vs 7075
| Alloy | Machinability | Strength (typ. UTS) | Best for |
|---|---|---|---|
| 6061-T6 | Excellent | ~310 MPa | The default: machined parts, welding, general fabrication |
| 6063-T5/T6 | Fair — sticks to tools | ~185 / 205 MPa | Extrusions, architectural profiles, decorative |
| 7075-T6 | Very good, gummy chips | ~570 MPa | Aerospace, tooling, high-load machined parts |
| 5052 / 5083 | Fair | ~230 / 290 MPa | Marine, sheet and plate — less common as bar |
Temper: T6 vs T651 vs T4
| Temper | Condition | Use |
|---|---|---|
| T6 | Solution heat-treated + artificial aged | Machined parts, general service — the standard |
| T651 | T6 stress-relieved for machining | Precision machining — flat and stable, better for CNC |
| T4 | Heat-treated, naturally aged | Forming, stamping, welded fabrication |
| T651 (6063-T5) | Extrusion temper | Profiles, architectural and window frames |
Surface Condition and Tolerance
- Mill finish: as-extruded or as-rolled surface, dimensional tolerance depends on size (often ±0.5 mm or more).
- Machined / turned: closer tolerance on diameter (h9 or better) for CNC work — request this if your parts are finish-critical.
- Straightness and length: confirm max straightness for automatic bar feeders, and specify SRL/fixed lengths vs coil.
Standards Buyers Quote
- ASTM B221: extruded bars, rods, and profiles — quote the shape.
- ASTM B221 for round/square, ASTM B209 for plate: confirm which form you actually need.
- EN 755 / EN 573: European equivalents — 6082-T6 is the common European general-purpose bar alloy.
- EN 10204 3.1 certs: include chemistry and tensile per lot on the PO.
Common Applications
- CNC-machined components: housings, brackets, spacers, fixtures.
- Weldments and frames in 6061-T6.
- Architectural and window/door profiles in 6063-T5/T6.
- Aerospace and tooling fixtures in 7075-T6.
RFQ Checklist
- Alloy and temper: 6061-T6, 6063-T5, 7075-T6 (be specific — “aluminum bar” alone is not a spec)
- Shape and size: round diameter or square side x tolerance
- Length: SRL / fixed length; straightness if for a bar feeder
- Surface: mill finish or machined; quantity, EN 10204 3.1 certs, destination / Incoterm
FAQ
6061 or 6063? 6061 for machining and welding; 6063 for extrusions and architectural profiles.
T6 or T651? T651 is stress-relieved — better dimensional stability for precision CNC; T6 is fine for general parts.
Why did my aluminum part crack during welding? 7075 and many high-strength alloys crack when welded — use 6061 for welded structures, or weld with appropriate filler and preheat.
Why Source Aluminum Bar from Yihang Metal
Yihang Metal supplies aluminum round and square bar in 6061, 6063, 6060, 6082, 7075, and 2024 to ASTM B221 / EN 755, in T4, T6, and T651 tempers with mill finish or machined surface and EN 10204 3.1 certs. Standard sizes typically ship in 25–35 days.
Ready to specify your aluminum bar? Send us the alloy, temper, shape and size, length, and quantity, and we will confirm mill availability and lead time with a fixed-price quote and test certificate. Email [email protected] or use the quote form on this page — our team replies within one business day.