Aluminium 7068 Properties
7068 aluminum alloy combines high strength, good ductility, and excellent corrosion resistance, making it the preferred choice for applications requiring lightweight yet strong materials.
7068 aluminum alloy is renowned for its exceptional strength-to-weight ratio, making it one of the strongest aluminum alloys available on the market. Initially developed for ordnance applications, it has since been widely used across various industries, including aerospace, automotive, medical, and recreational sectors.
Aluminium 7068 Chemical Composition
| Element | Percentage |
| Zinc (Zn) | 7.5–8.5% (Primary strengthener) |
| Magnesium (Mg) | 2.2–3.0% |
| Copper (Cu) | 1.6–2.4% |
| Chromium (Cr) | Trace Element |
| Zirconium (Zr) | Trace Element |
| Iron (Fe) | Trace Element |
| Silicon (Si) | Trace Element |
| Titanium (Ti) | Trace Element |
Aluminium 7068 Physical Properties
| Property | Value |
| Density | ~2.82 g/cm³ |
| Melting Range | 477–635°C (890–1175°F) |
| Electrical Conductivity | ~33% IACS |
| Thermal Conductivity | ~130 W/m·K |
Aluminium 7068 Mechanical Properties (T6 Temper)
| Property | Value |
| Ultimate Tensile Strength (UTS) | 710–750 MPa (103–109 ksi) |
| Yield Strength | 650–690 MPa (94–100 ksi) |
| Elongation at Break | 8–12% (in 50 mm) |
| Hardness | ~85–90 HRB (Rockwell B) |
| Fatigue Strength | ~230 MPa (33 ksi) at 10⁸ cycles |
| Modulus of Elasticity | 71 GPa (10.3 × 10⁶ psi) |
| Fracture Toughness | ~25–30 MPa√m (depends on temper) |
Aluminium 7068 Corrosion Resistance
- General Corrosion Resistance: Moderate; lower than 5xxx/6xxx alloys.
- Stress Corrosion Cracking (SCC): Susceptible in T6 temper; T7 can improve SCC resistance.
- Protection: Typically treated with anodizing or coatings to withstand harsh environments.
Aluminium 7068 Manufacturing and Processing
- Machinability: Good when using appropriate tools (carbide tools recommended).
- Weldability: Poor; prone to hot cracking. Friction stir welding or specialized techniques are recommended.
- Formability: Limited in high-strength tempers; best in annealed (O) condition.
- Availability: Extrusions, forgings, plates, bars.
Aluminium 7068 Applications
Due to its high strength and excellent properties, Aluminium 7068 is used in various applications, including:
- Aerospace: Structural components such as fuselage structures and wing parts.
- Automotive: High-performance components such as valve bodies and connecting rods.
- Medical Equipment: Prosthetics requiring strength and lightweight characteristics.
- Recreational Products: Equipment such as bicycles and mountaineering gear.
- Military: Armor components, missile parts.
Aluminium 7068 Comparison with Other Alloys
| Property | 7068-T6 | 7075-T6 | 6061-T6 |
| Tensile Strength (MPa) | 710–750 | 520–570 | 310–340 |
| Yield Strength (MPa) | 650–690 | 460–490 | 270–300 |
| Density (g/cm³) | 2.82 | 2.81 | 2.70 |
| Corrosion Resistance | Moderate | Moderate | Good |
Aluminium 7068 Heat Treatment and Tempers
The 7068 alloy responds well to heat treatment, with various tempers offering different balances of strength and ductility:
- T6 Temper: Provides high static strength but lower toughness and ductility. Increased susceptibility to stress corrosion cracking makes it less suitable for low-temperature applications.
- T73 Temper: Offers lower strength but higher fracture toughness and excellent resistance to stress corrosion cracking and erosion, making it ideal for applications where durability is a priority.
- T76 Temper: Balances strength and corrosion resistance, making it suitable for applications requiring a compromise between the two.
- Corrosion Resistance: This alloy exhibits good corrosion resistance, comparable to 7075 aluminum. T73 temper, in particular, provides excellent resistance to stress corrosion cracking, making it suitable for harsh environments.
Aluminium 7068 Standards and Specifications
- AMS: AMS 4331 (Aerospace Material Specification).
- ASTM: B947 (7068 product standard).
Aluminium 7068 Limitations
- Higher cost than 7075/6061 due to specialized processing.
- Requires protective coatings in corrosive environments.
- Fusion welding is not recommended without post-weld heat treatment.
Aluminium 7068 excels in applications requiring ultra-high strength and lightweight properties, outperforming 7075 in critical aspects. It performs best in controlled environments where corrosion can be managed, and its mechanical properties justify the trade-offs in cost and machinability.