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Should I use 6061 or 7075 aluminum?
Use 6061-T6 for most machined parts. It welds, anodizes cleanly, resists corrosion better, and costs about half as much as 7075-T6. Choose 7075-T6 when strength sets the design: it runs about 83 ksi (572 MPa) tensile versus 45 ksi (310 MPa), nearly twice 6061-T6, but it cannot be fusion welded and should be anodized for outdoor service.
Aluminum 6061-T6
Aluminum 7075-T6
By the numbers
Priced on the same representative part: plate, cnc machining, 50 pcs.
Tensile strengthMPa
6061-T6
310
7075-T6
572
Yield strengthMPa
6061-T6
276
7075-T6
503
Densityg/cm³
6061-T6
2.7
7075-T6
2.81
Max service temp°C
6061-T6
150
7075-T6
120
Elongation%
6061-T6
12
7075-T6
11
Raw material cost$/kg
6061-T6
7
7075-T6
13
Which should you pick?
Pick 6061-T6 when
- The part is welded now or may be welded later
- You need clear, black or color-matched anodize
- Service is outdoor or wet and the part gets only a light coating
- You need sheet, tube or extruded shapes as well as bar and plate
Pick 7075-T6 when
- Required yield is above about 40 ksi (276 MPa); 7075-T6 yields near 73 ksi (503 MPa)
- The part is bolted or bonded, never welded
- Cyclic loads drive the design, as in drone, robot and bicycle structures
- The part will be anodized anyway, which covers its weaker corrosion resistance
Key differences
| 6061-T6 | 7075-T6 | |
|---|---|---|
| Weldability | TIG or MIG with 4043 or 5356 filler; the heat-affected zone drops to about 24 ksi (165 MPa) | Not fusion weldable; TIG and MIG welds hot-crack. Friction stir welding only |
| Anodize response | Clean clear, black and dyed colors | Clear anodize tints yellow or bronze; black dyes well |
| Corrosion | Holds up bare indoors and in mild outdoor exposure | Lower general resistance; T6 is prone to stress corrosion cracking, so specify T73 or T7351 under sustained stress |
| Bending | Inside radius of 1.5–3× thickness in T6 | Poor formability; treat it as a machining alloy |
| Stock forms | Bar, plate, sheet, tube and extrusions | Mostly bar and plate, including T651 stress-relieved plate |
| Relative material cost | Baseline | Roughly 2× per pound |
Questions
Is 7075 aluminum stiffer than 6061?
Barely. Modulus is about 10.4 Msi (71.7 GPa) for 7075-T6 versus 10.0 Msi (68.9 GPa) for 6061-T6, so a deflection-limited part bends almost the same amount in either alloy. 7075 helps only when strength, not stiffness, sets the section size.
Is 7075 harder to machine than 6061?
No. Both machine fast. 7075-T6 is harder, about 150 HB versus 95 HB, and tends to give shorter chips and a finer finish. Machining time is usually similar, so material price is what separates the two.
Can 7075 aluminum be welded?
Not by TIG or MIG. Fusion welds hot-crack and lose most of the T6 strength. Friction stir welding works. Design bolted or bonded joints, or switch to 6061-T6 if the part must be welded.
Which is better for outdoor parts, 6061 or 7075?
6061-T6. It has better general corrosion resistance and no practical stress corrosion concern. If 7075 is needed outdoors, anodize or chem film it and specify T73 or T7351 for parts under sustained tensile stress.
Try both on your part.
The builder prices the same geometry in every suitable process and material, with DFM for each.