6061 vs 7075 Aluminum
6061 is the general-purpose aluminum: strong enough for most structures, easy to machine, weldable, anodizes cleanly and costs the least. 7075 is the high-strength aerospace alloy: nearly twice the yield strength at a similar density, but it cannot be fusion welded, corrodes faster and costs more.
The decision is usually simple. If the part will be welded, or is stiffness-limited rather than strength-limited, use 6061. If it is strength- or fatigue-limited and will be fastened or bonded, 7075 saves weight.
| Property | 6061-T6 | 7075-T6 |
|---|---|---|
| Alloy family | 6xxx (Mg-Si) | 7xxx (Zn-Mg-Cu) |
| Tensile (T6) | 310 MPa (45 ksi) | 572 MPa (83 ksi) |
| Yield (T6) | 276 MPa (40 ksi) | 503 MPa (73 ksi) |
| Density | 2.70 g/cm³ | 2.81 g/cm³ |
| Elongation (T6) | 12-17% | 9-11% |
| Hardness | ~95 HB | ~150 HB |
| Weldability | Good | Poor (fusion welding) |
| Corrosion resistance | Good | Lower; often anodized or clad |
| Relative cost | Baseline | Higher |
| Typical uses | Structural, frames, general fab | Aerospace, high-stress parts, molds |
Typical values for the stated conditions. Confirm against the mill certificate and your spec.
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Attach a drawing (PDF or STEP) or describe the part; a U.S. shop that fits quotes it.
Decision matrix
A check marks the side with the edge on that dimension.
| Dimension | 6061-T6 | 7075-T6 |
|---|---|---|
| Machining | Good; fast, clean chips in T6 | ✓ Excellent; harder, holds a finer finish |
| Welding | ✓ Excellent with 4043/5356 filler | Not recommended; hot cracking |
| Forming | ✓ Good in O/T4; fair in T6 | Poor; form in O and heat treat after |
| Strength | 276 MPa yield | ✓ 503 MPa yield, better fatigue |
| Corrosion resistance | ✓ Good; anodize for marine | Fair; prone to stress-corrosion in T6, use T73 |
| Finishing | ✓ Anodizes uniformly, dyes well | Anodizes; duller, darker, less uniform colour |
| Material cost | ✓ Baseline aluminum | About 1.5-2x per pound |
| Availability | ✓ Stocked everywhere, all forms | Plate and bar common; sheet and extrusions less so |
Choose 6061-T6 when
- The part will be welded
- Stiffness or geometry, not strength, sizes the part (both alloys have the same modulus)
- Corrosion resistance matters and the part will not be anodized
- Cost, lead time or a full range of stock shapes matter
Choose 7075-T6 when
- The part is strength- or fatigue-limited and weight matters: aircraft fittings, suspension parts, high-load brackets
- Higher hardness for wear or a finer machined finish, such as mold plates and fixtures
- The assembly is fastened, bonded or one piece, never welded
- Use the T73 or T7351 temper where stress-corrosion cracking is a risk
Frequently asked questions
- Is 7075 stronger than 6061?
- Yes, substantially. In the T6 temper 7075 has roughly double the tensile and yield strength of 6061 (about 572 vs 310 MPa tensile). 7075 is the high-strength aerospace alloy; 6061 is the general-purpose workhorse.
- Which is more weldable?
- 6061 by far. It welds readily (commonly with 4043 or 5356 filler). 7075 is considered poorly weldable by fusion: its high zinc content causes hot cracking, so 7075 parts are usually fastened or bonded rather than welded.
- When should I use 6061?
- Most of the time: structural shapes, frames, brackets, enclosures, and anything you need to weld or that benefits from better corrosion resistance and lower cost. Reach for 7075 only when you need maximum strength-to-weight and can fasten rather than weld.
- Is 7075 harder to machine than 6061?
- No. 7075-T6 is harder and machines to a better finish with less burr; many shops prefer it. Its chips are less gummy than 6061. The extra cost of 7075 is the material, not the machining.
