Primary aerospace structure
Wing skins, fuselage frames, bulkheads, longerons, ribs. The default for load-bearing aircraft aluminum.
Aerospace aluminum · UNS A97075
Aluminum 7075-T6
The high-strength aerospace aluminum. Zinc as the primary alloying element pushes 7075-T6 to ~85% higher tensile strength than 6061-T6 — at a small density penalty. Standard for airframes, weapon platforms, bike frames, and high-stress aluminum applications.
UTS
572 MPa
Density
2.81 g/cc
Modulus
71.7 GPa
Mach.
70 /100
When to use
Pick 7075 when 6061 isn’t strong enough — and weight still matters.
7075-T6 has a yield strength of 503 MPa (73 ksi) — roughly twice 6061-T6. That’s why it’s the default for primary aircraft structures: wing skins, fuselage frames, bulkheads, and load-carrying brackets. It’s also the bicycle-frame and aluminum-firearm-frame standard.
The catches: less corrosion resistance than 6061, much harder to weld (zinc-magnesium alloys are crack-sensitive), and roughly 30% more expensive. The T651 temper is identical strength to T6 but stress-relieved by stretching — strongly preferred for plate that will be machined into thin-wall parts.
Strengths
Why aerospace specifies it.
- Strength rivals mild steelUTS 572 MPa is comparable to 1018 cold-drawn steel — at ⅓ the weight.
- Excellent fatigueEndurance limit ~159 MPa at 5×10⁸ cycles. Standard for cyclically loaded airframe parts.
- Anodizes wellType II clear and color, Type III hardcoat. Corrosion protection + cosmetic finish.
- Machinability 70/100Slightly worse than 6061 — chips break differently — but still very fast cutting.
- Forgings widely availableMajor aerospace forging stock material. Parts with grain flow and properties forgings provide.
Trade-offs
What 6061 does better.
- Corrosion resistanceStress-corrosion cracking susceptibility in T6. T73 and T7351 tempers exist for SCC-prone applications, at lower strength.
- WeldingGenerally not weldable — heat-affected zone cracks. Mechanical fasteners only. (T6 specifically; weldable variants exist with sub-strength joints.)
- Cost~30% more than 6061 per pound. Multi-axis machined airframe parts often start as plate, with high scrap rates.
- Anodizing color depthT6 produces darker anodize than 6061 due to copper content. Cosmetic appearance differs across batches.
- Heat-soak limitsT6 properties degrade above 120 °C (250 °F). For elevated temp, look at 2618 or step up to titanium.
Specs
Mechanical, physical & chemical data.
Mechanical
Properties (T6)
| Ultimate tensile strength | 572 MPa (83 ksi) |
|---|---|
| Yield strength (0.2% offset) | 503 MPa (73 ksi) |
| Elongation at break | 11% |
| Modulus of elasticity | 71.7 GPa |
| Shear modulus | 26.9 GPa |
| Shear strength | 331 MPa |
| Poisson's ratio | 0.33 |
| Hardness | 150 HB (~87 HRB) |
| Fatigue strength 5 × 10⁸ cycles, R = -1 | 159 MPa |
T651 (stretch-relieved) values are equivalent. T7351 trades ~10% strength for stress-corrosion resistance.
Physical & thermal
Properties at room temp
| Density | 2.81 g/cc (0.102 lb/in³) |
|---|---|
| Melting range | 477 – 635 °C |
| Specific heat | 0.960 J/g·°C |
| Thermal conductivity | 130 W/m·K |
| CTE (20–100 °C) | 23.4 µm/m·°C |
| Electrical conductivity | 33% IACS |
| Magnetic | Non-magnetic |
Thermal conductivity ~80% of 6061 — slightly less heat dissipation, otherwise machines very similarly.
Composition
Chemistry, weight %
| Zinc (Zn) | 5.1 – 6.1 |
|---|---|
| Magnesium (Mg) | 2.1 – 2.9 |
| Copper (Cu) | 1.2 – 2.0 |
| Chromium (Cr) | 0.18 – 0.28 |
| Iron (Fe) | 0.50 max |
| Silicon (Si) | 0.40 max |
| Manganese (Mn) | 0.30 max |
| Titanium (Ti) | 0.20 max |
| Aluminum (Al) | balance (~90%) |
The Zn-Mg-Cu system gives the strength; the copper is also the reason 7075 is less corrosion-resistant than copper-free aluminums.
Specifications
Common purchase specs.
AMS 4045
Sheet, plate — T651
AMS 4078
Plate — T7351 (overaged)
AMS 4126
Forgings — T6
AMS 4124
Bar, rod, wire — T7351 (rolled or cold finished)
ASTM B221
Extruded bar, rod, profiles
ASTM B211
Bar, rod, wire — rolled or cold finished
MIL-A-22771
Forgings — T6 and T73
EN AW-7075
European equivalent
Machining
How we cut it.
7075 cuts almost as easily as 6061 — chips break a little stringier, but with sharp tools it’s a non-issue. The bigger machining concern is residual stress in plate stock. Always specify T651 for thin-wall machined parts.
Cutting speed
1,200 – 3,000 SFM with carbide. Slightly less than 6061 — chip control favors moderate speeds.
Feed rate
Aggressive. Same rules as 6061 — keep the chip continuous.
Tooling
Polished uncoated carbide for finishing. PCD for high-volume.
Coolant
Flood, light oil. Some shops run dry with MQL on smaller parts.
Use T651 for plate
Stretch-relieved plate machines straight. Non-relieved plate (T73 or T6) springs after machining.
Watch deep pockets
Aluminum's high CTE + machining heat can warp thin-wall pockets. Roughing pass + cool-down + finish pass.
Threading
Roll forms preferred. Cut taps work but a thread insert is bulletproof in 7075 for repeated assembly.
Surface finish
Easy to hold 32 µin Ra. 16 µin needs a sharp finishing tool and light DOC.
Applications
Where 7075 shows up.
Defense & weapons
Rifle and pistol frames, tactical mounts, military hardware. The strength and weight balance 4140 can’t match.
Sporting & precision
High-end bicycle frames, rock-climbing hardware, precision optics mounts. Where stiffness-to-weight is the dominant requirement.
Compare
Related materials.
General purpose
6061-T6 →
Easier to machine, weld, and corrosion-resist — at ~half the strength.
Higher specific strength
Ti-6Al-4V →
Higher absolute strength + better corrosion + temperature capability — at higher cost.
Strength + cost
4140 Steel →
More strength, much cheaper, much heavier. Only when weight isn’t critical.
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