The 7000 Series aluminium alloys are high-strength, heat-treatable aluminium alloys in which zinc (Zn) is the primary alloying element, typically combined with magnesium (Mg) and copper (Cu).
These alloys deliver the highest strength among all aluminium alloy families, often comparable to or exceeding mild steel, while maintaining a much lower density.
Because of their exceptional strength-to-weight ratio, fatigue resistance, and structural stability, 7000 series alloys are extensively used in aerospace, defense, high-performance automotive, sporting equipment, and critical structural applications.
Typical Chemical Composition (7000 Series)
| Element | Typical Range (%) |
|---|---|
| Aluminium (Al) | Balance |
| Zinc (Zn) | 4.0 – 8.5 |
| Magnesium (Mg) | 1.0 – 3.0 |
| Copper (Cu) | 0.1 – 2.0 |
| Chromium (Cr) | 0.05 – 0.30 |
| Silicon (Si) | ≤ 0.40 |
| Iron (Fe) | ≤ 0.50 |
| Manganese (Mn) | ≤ 0.30 |
| Titanium (Ti) | ≤ 0.20 |
Mechanical & Physical Properties
(Typical values – vary by temper such as T6, T73, T76)
Physical Properties
Density: ~2.80 g/cm³
Melting Point: ~475 – 635°C
Thermal Conductivity: 130 – 160 W/m·K
Electrical Conductivity: Moderate
Elastic Modulus: ~71 GPa
Coefficient of Thermal Expansion: ~23 × 10⁻⁶ /°C
Non-magnetic
Mechanical Properties
Tensile Strength: 450 – 750 MPa
Yield Strength: 400 – 680 MPa
Elongation: 5 – 15%
Brinell Hardness: 120 – 180 HB
Fatigue Strength: Excellent
Fracture Toughness: High (grade-dependent)
7075-T6 approaches the strength of structural steel at one-third the weight.
Strengthening & Metallurgical Behavior
Strengthening Mechanism
Precipitation (age) hardening
Formation of MgZn₂ precipitates during aging
Heat Treatment Process
Solution Heat Treatment
Quenching
Artificial Aging (T6, T73, T76 tempers)
Metallurgical Characteristics
Very fine precipitate structure
High strength but reduced ductility compared to other series
Susceptible to stress corrosion cracking (improved in over-aged tempers)
Key Characteristics
1. Highest Strength Aluminium Alloy
Stronger than all other aluminium families
Ideal replacement for steel where weight saving is critical
2. Exceptional Fatigue Resistance
Excellent under cyclic and dynamic loading
Widely used in aircraft and racing components
3. High Hardness & Wear Resistance
Suitable for high-load and high-stress components
4. Good Dimensional Stability
Maintains shape under mechanical and thermal stress
5. Limited Corrosion Resistance (Compared to 5xxx/6xxx)
Requires surface protection (anodizing, cladding, coating)
Improved corrosion resistance in T73 / T76 tempers
Refining & Processing Properties
Heat Treatment
Highly responsive to heat treatment
Wide strength range achievable
Machinability
Excellent
Produces clean chips
Preferred for precision aerospace machining
Weldability
❌ Generally poor
Welding may reduce strength and corrosion resistance
Mechanical fastening preferred
Surface Treatments
Anodizing (protective & hard anodizing)
Alclad coatings for aerospace sheets
Shot peening for fatigue improvement
Available Forms of 7000 Series Aluminium
Plates & Sheets (Rolled / Alclad)
Bars & Rods
Forgings (Blocks, Rings, Shafts)
Extruded Profiles (Limited)
Precision Machined Components
Billets & Blooms
Aerospace-grade Custom Shapes
Applications of 7000 Series Aluminium
1. Aerospace & Defense
Aircraft wings & fuselage frames
Landing gear components
Missile structures
Aerospace fasteners
2. High-Performance Automotive
Racing chassis
Suspension arms
Structural brackets
3. Sports & Recreation
Bicycle frames
Climbing equipment
Golf clubs
High-end sporting goods
4. Tooling & Industrial Equipment
Molds
High-load fixtures
Precision jigs
5. Military & Structural Systems
Armor components
Structural reinforcements
Tactical equipment
Advantages of 7000 Series Aluminium
Highest strength-to-weight ratio among aluminium alloys
Steel-like strength with aluminium weight
Excellent fatigue performance
Outstanding machinability
Heat-treatable for tailored properties
Critical for aerospace safety standards
Why Choose 7000 Series Aluminium?
The 7000 Series aluminium alloys are the ultimate choice for applications demanding extreme strength, precision, and fatigue resistance.
When weight reduction, structural integrity, and performance under stress are critical, 7000 series alloys outperform all other aluminium families.
They are the material of choice in aerospace, defense, motorsport, and elite engineering, where failure is not an option and performance is paramount.