7475 aluminum plate sheet
7475 aluminum plate sheet is a premium aerospace-grade wrought alloy known for combining very high strength, excellent fracture toughness, and good fatigue resistance in thick and thin gauges alike. Built on an Al-Zn-Mg-Cu chemistry similar to other 7xxx alloys, 7475 is distinguished by refined impurity control and processing routes that help deliver superior damage tolerance-one of the reasons it is frequently specified for critical aircraft structures where reliability under cyclic loading matters as much as peak strength.
For customers comparing high-strength aluminum plate and sheet options, 7475 stands out when the design target includes high static strength plus toughness, especially in sheet and plate products where crack growth behavior and stress-corrosion performance can drive service life.
Features at a Glance
| Feature | What it Means in Practice | Typical Benefit |
|---|---|---|
| Very high strength (7xxx series) | Strong response to precipitation hardening | Weight reduction for strength-driven designs |
| High fracture toughness | Better resistance to crack initiation and growth | Improved damage tolerance for safety-critical parts |
| Good fatigue performance | Handles repeated loading well | Longer service life in cyclic stress environments |
| Strong aerospace pedigree | Widely used in aircraft skins and structural elements | Mature specifications and processing knowledge |
| Good machinability (in heat-treated conditions) | Clean chip formation and stable cutting | Efficient manufacturing for plate components |
| Moderate corrosion resistance (vs. 5xxx/6xxx) | Often protected by cladding/coatings | Reliable performance with proper surface engineering |
Note: 7475 is typically selected when toughness and fatigue are prioritized alongside strength. If maximum corrosion resistance without coatings is the main goal, other alloy families may be more suitable.
Typical Chemical Composition
7475 is an Al-Zn-Mg-Cu alloy. Composition limits can vary slightly by standard and producer control practices; the table below reflects commonly used nominal ranges.
| Element | Typical Range (wt.%) | Role in the Alloy |
|---|---|---|
| Zinc (Zn) | 5.2–6.2 | Primary strength contributor via precipitates |
| Magnesium (Mg) | 2.0–2.7 | Strengthening; works synergistically with Zn |
| Copper (Cu) | 1.2–1.9 | Boosts strength; influences SCC behavior |
| Chromium (Cr) | 0.18–0.25 | Grain structure control; improves toughness |
| Manganese (Mn) | ≤0.06 | Impurity control / minor effects |
| Silicon (Si) | ≤0.10 | Kept low for toughness and cleanliness |
| Iron (Fe) | ≤0.12 | Kept low to reduce brittle intermetallics |
| Titanium (Ti) | ≤0.06 | Grain refinement |
| Aluminum (Al) | Balance | Base metal |
Product Forms and Common Tempers
7475 is supplied mainly as plate and sheet, frequently in tempers tailored to balance strength, toughness, and corrosion performance.
| Temper (common) | General Description | Why Customers Choose It |
|---|---|---|
| T6 | Solution heat treated and artificially aged | High strength for static-load designs |
| T73 / T7351 / T7651 (varies by form) | Over-aged variants | Improved stress-corrosion cracking resistance and toughness (often at some strength cost) |
| O (annealed) | Soft, maximum ductility | Forming trials, deep forming, or subsequent heat treatment |
Availability can differ by mill and thickness range; for aerospace work, customers often specify temper and testing requirements directly to the governing standard.
Typical Mechanical Performance (Reference Values)
Mechanical properties depend strongly on thickness, direction (L/LT/ST), temper, and product form. The values below are representative ranges often used for preliminary engineering discussions; project-specific design should rely on certified mill test reports and applicable standards.
| Property | Typical Range (Sheet/Plate, heat-treated) | Notes |
|---|---|---|
| Ultimate tensile strength, UTS | 510–600 MPa | Higher in peak-aged conditions, thickness dependent |
| Yield strength, YS (0.2%) | 430–520 MPa | Temper and thickness strongly influence |
| Elongation | 6–12% | Higher elongation generally correlates with higher toughness tempers |
| Fracture toughness (plane strain), K_IC | 25–40 MPa√m | Common driver for selecting 7475 vs. alternatives |
| Density | ~2.81 g/cm³ | Typical for Al-Zn-Mg-Cu alloys |
| Elastic modulus | ~71 GPa | Similar to most aluminum alloys |
Technical Specifications and Supply Options
Customers usually purchase 7475 to an aerospace standard (or equivalent), and then define additional requirements around ultrasonic inspection, grain direction, and property targets.
| Parameter | Typical Customer Specification Considerations |
|---|---|
| Thickness range | Sheet and plate ranges vary by producer; thin gauge for skins, thicker plate for machined structure |
| Dimensional tolerances | Tight tolerance plate for machining efficiency; flatness requirements for skins and panels |
| Surface condition | Mill finish, clad options, or pre-treated surfaces depending on joining and corrosion strategy |
| Inspection | Ultrasonic testing for plate; surface inspection for sheet criticality |
| Certification | Full traceability, heat/lot control, and mechanical testing per order |
If your application is fatigue- or fracture-critical, specifying grain orientation and requiring directionally tested properties (L, LT, ST) can be as important as selecting the alloy itself.
Why 7475 Is Valued in Aerospace Structures
7475 gained its reputation by delivering a practical balance of strength and damage tolerance. In aircraft structures, a material is rarely chosen solely for its maximum tensile strength. Engineers care about how the alloy behaves when real-world variables show up: small manufacturing defects, fastener holes, impacts, and long-term cyclic loading.
7475's controlled chemistry and processing help improve resistance to crack growth, which supports:
| Design Concern | How 7475 Helps | Typical Outcome |
|---|---|---|
| Crack initiation at holes/edges | Cleaner microstructure and good toughness | Increased inspection intervals potential |
| Fatigue crack growth | Damage tolerance focus | Better life under repeated loading |
| Thick-section integrity | Plate toughness characteristics | Confidence in machined monolithic parts |
Applications
7475 aluminum plate sheet is primarily used where high-performance structural behavior is required and where protective finishing systems are acceptable.
| Industry | Typical Components | Why 7475 Fits |
|---|---|---|
| Aerospace (primary) | Wing skins, fuselage skins, shear webs, stringers, frames, structural panels | High strength-to-weight plus toughness and fatigue resistance |
| Defense and high-performance aviation | Structural plates, load-bearing panels, machined components | Robust performance under demanding duty cycles |
| Motorsport and high-end engineering | Lightweight structural plates, brackets, stiff panels | Strength and stiffness with manageable machining |
| Tooling and fixtures (select cases) | High-load fixtures, precision plates | Stable performance and good machinability when strength is needed |
Where corrosion exposure is severe (marine splash zones, aggressive industrial atmospheres), 7475 is typically paired with cladding, anodizing, primer/paint systems, and proper sealing.
Processing, Joining, and Finishing Notes
| Topic | Practical Guidance |
|---|---|
| Machining | Performs well in heat-treated tempers; use sharp tools and manage heat input to maintain surface integrity |
| Forming | Easier in softer tempers; complex forming is often done before final heat treatment |
| Welding | Generally not preferred for highly loaded welded structures in 7xxx alloys; consider mechanical fastening, riveting, or bonded joints where appropriate |
| Corrosion protection | Use anodizing, conversion coatings, primers/paints; consider clad products when available |
| Stress-corrosion strategy | Select an appropriate temper (often over-aged variants) and maintain good surface protection and drainage design |
Selecting 7475: When It's the Right Choice
7475 aluminum plate sheet is a strong candidate when your project needs high strength without sacrificing toughness, and when service conditions involve fatigue, crack-growth sensitivity, or safety-critical load paths. It is especially compelling for aircraft skins and structural panels where damage tolerance is a design philosophy rather than an afterthought.