Introduction
7075 aluminum alloy is known as an ultra-high strength aluminum alloy and is one of the most important structural materials in the aerospace and aviation industries. It belongs to the Al-Zn-Mg-Cu (7xxx) series, where zinc is the primary alloying element.
7075 is characterized by a yield strength approaching its tensile strength (high yield ratio) and a very high specific strength (strength-to-weight ratio). However, its plasticity and high-temperature strength are relatively low, making it best suited for load-bearing structural components used at ambient temperature or below 120°C.
Compared to the 6xxx series alloys such as 6061 and 6063, 7075 offers significantly higher strength at the cost of reduced weldability and extrudability. It is easy to machine, has good corrosion resistance, and high toughness.
Reference standards: GB/T 3190-2020, GB/T 3191-2019, GB/T 3880.2-2012, JIS H4000-1999, JIS H4080-1999, ASTM (UNS A97075 / AA 7075)
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Chemical Composition
Reference: GB/T 3190-2020 / AA (Aluminum Association) / UNS A97075
| Element | Si (%) | Fe (%) | Cu (%) | Mn (%) | Mg (%) | Cr (%) | Zn (%) | Ti (%) | Al (%) |
|---|---|---|---|---|---|---|---|---|---|
| 7075 | ≤ 0.40 | ≤ 0.50 | 1.20–2.00 | ≤ 0.30 | 2.10–2.90 | 0.18–0.28 | 5.10–6.10 | ≤ 0.20 | Balance |
Key alloying elements:
- Zinc (Zn, 5.1–6.1%): Primary strengthening element. Forms MgZn₂ (eta phase) precipitates during aging, providing the exceptional strength of 7075.
- Magnesium (Mg, 2.1–2.9%): Works with Zn to form MgZn₂ strengthening precipitates.
- Copper (Cu, 1.2–2.0%): Enhances strength and stress corrosion cracking resistance.
- Chromium (Cr, 0.18–0.28%): Controls grain structure and improves stress corrosion resistance.
Temper Designations Explained
| Temper Code | Description |
|---|---|
| O | Annealed (fully soft) |
| T6 | Solution heat treated + artificial aging (peak strength) |
| T62 | Solution heat treated + artificial aging (applied to O or F temper material) |
| T6510 / T6511 | T6 + controlled stretching for stress relief (T6511 allows minor straightening) |
| T73 | Solution heat treated + over-aged (improved stress corrosion resistance, lower strength than T6) |
| T73510 / T73511 | T73 + controlled stretching for stress relief |
| T1 | Cooled from hot forming + naturally aged |
| T3 | Solution heat treated + cold worked + naturally aged |
| T4 | Solution heat treated + naturally aged |
| T5 | Cooled from hot forming + artificially aged |
| T7 | Solution heat treated + over-aged |
| T8 | Solution heat treated + cold worked + artificially aged |
7075-T6 is the most commonly specified temper: solution heat treatment followed by artificial aging, delivering peak strength. It is the standard delivery condition for extruded bars and structural stock.
Mechanical Properties by Bar Size (GB/T 3191-2019)
| Product / Size | Temper | Tensile Strength σb (MPa) | Yield Strength σs (MPa) | Elongation δ (%) | Hardness (HBW) |
|---|---|---|---|---|---|
| Bar, d ≤ 200 mm | O (annealed) | ≥ 275 | ≥ 165 | ≥ 10 | 60 |
| Bar, d ≤ 25 mm | T6 / T62 / T6510 / T6511 | ≥ 540 | ≥ 480 | ≥ 7 | 150 |
| Bar, 25 < d ≤ 100 mm | T6 / T62 / T6510 / T6511 | ≥ 560 | ≥ 500 | ≥ 7 | 150 |
| Bar, 100 < d ≤ 150 mm | T6 / T62 / T6510 / T6511 | ≥ 550 | ≥ 440 | ≥ 5 | 150 |
| Bar, 150 < d ≤ 200 mm | T6 / T62 / T6510 / T6511 | ≥ 440 | ≥ 400 | ≥ 5 | 150 |
| Bar, d ≤ 25 mm | T73 / T73510 / T73511 | ≥ 485 | ≥ 420 | ≥ 7 | 135 |
| Bar, 25 < d ≤ 75 mm | T73 / T73510 / T73511 | ≥ 475 | ≥ 390 | ≥ 6 | 135 |
| Bar, 75 < d ≤ 100 mm | T73 / T73510 / T73511 | ≥ 470 | ≥ 390 | ≥ 6 | 135 |
| Bar, 100 < d ≤ 150 mm | T73 / T73510 / T73511 | ≥ 440 | ≥ 360 | ≥ 6 | 135 |
d = diameter of round bar, or thickness of square/hex bar (mm). Available supply tempers: O, T1, T6, T6510, T6511, T73, T73510, T73511.
Key Material Characteristics
- Ultra-high strength: Highest strength among common aluminum alloys; T6 temper achieves ≥ 540 MPa tensile strength for small-diameter bars
- High yield ratio: Yield strength approaches tensile strength, indicating efficient use of material in structural design
- Good machinability: Easy to machine with good surface finish; wear resistance is good
- Good corrosion resistance: Better than 2xxx series; Cr addition improves stress corrosion resistance
- High toughness: Good impact resistance for a high-strength alloy
- Temperature limitation: Best used at ambient temperature or below 120°C; not suitable for elevated-temperature structural applications
7075-T6 vs T73: When to Choose Which
| Criteria | 7075-T6 | 7075-T73 |
|---|---|---|
| Tensile strength (d ≤ 25 mm) | ≥ 540 MPa | ≥ 485 MPa |
| Yield strength (d ≤ 25 mm) | ≥ 480 MPa | ≥ 420 MPa |
| Stress corrosion resistance | Moderate | Excellent |
| Best for | Maximum strength applications | Environments with stress corrosion risk (marine, chemical) |
7075 vs Other Aluminum Alloys
| Alloy / Temper | Tensile Strength (MPa) | Yield Strength (MPa) | Weldability | Typical Use |
|---|---|---|---|---|
| 7075-T6 | ≥ 540 | ≥ 480 | Poor | Aerospace structures, high-stress machined parts |
| 6061-T6 | ~310 | ~276 | Good | General structural, fasteners, machined parts |
| 6063-T6 | ~215 | ~170 | Good | Architectural extrusions, decorative profiles |
Applications of 7075 Aluminum Alloy
- Aerospace & Aviation — aircraft frames, wing spars, fuselage skins, bulkheads, and structural fittings; one of the most critical structural materials in this sector
- Defense & Military — armor plates, weapon components, military vehicle structures
- High-performance sporting goods — bicycle frames, climbing equipment, archery bows, ski bindings
- Precision machined components — molds, jigs, fixtures, and high-stress mechanical parts
- Automotive motorsport — racing car chassis components and suspension parts
- Fasteners — high-strength aluminum bolts and structural fasteners where weight reduction is critical
Standards reference: GB/T 3190-2020 | GB/T 3191-2019 | GB/T 3880.2-2012 | JIS H4000-1999 | JIS H4080-1999 | ASTM (UNS A97075 / AA 7075)
Content authorized for publication by FULLERKREG.