7178-T76; 7178-T7651 Aluminum alloy,Aluminum 7178-T76; 7178-T7651 alloy，E FORU

### **7178-T76 / 7178-T7651 Aluminum Alloy: High-Strength with Enhanced Corrosion Resistance** **7178-T76 and 7178-T7651** are specialized tempers of the ultra-high strength 7178 aluminum alloy, offering an improved balance between mechanical strength and corrosion resistance. These tempers provide enhanced resistance to exfoliation corrosion and stress corrosion cracking while maintaining high strength levels for critical aerospace applications. --- #### **1. Chemical Composition** | Element | Content (%) (Typical) | Role in the Alloy | | :--- | :--- | :--- | | **Zinc (Zn)** | 6.3 - 7.3 | Primary strengthening element through formation of MgZn₂ precipitates | | **Magnesium (Mg)** | 2.4 - 3.1 | Enhances strength and age-hardening response | | **Copper (Cu)** | 1.6 - 2.4 | Improves strength and stress corrosion cracking resistance | | **Chromium (Cr)** | 0.18 - 0.28 | Controls grain structure and improves toughness | | **Iron (Fe)** | ≤ 0.50 | Impurity - controlled for improved consistency | | **Silicon (Si)** | ≤ 0.40 | Impurity - controlled for improved ductility | | **Manganese (Mn)** | ≤ 0.30 | - | | **Titanium (Ti)** | ≤ 0.20 | - | | **Other Elements** | ≤ 0.05 each; ≤ 0.15 total | - | | **Aluminum (Al)** | Balance | Base metal | --- #### **2. Understanding the T76 and T7651 Tempers** **T76 Temper:** - Solution heat-treated and artificially over-aged to an intermediate level - Enhanced corrosion resistance compared to T6 temper - Good balance of strength and corrosion resistance **T7651 Temper:** - Solution heat-treated, stress-relieved by stretching, and artificially over-aged - Specifically for plate products - Improved dimensional stability for machining - Reduced residual stresses **Key Characteristics:** - Excellent exfoliation corrosion resistance - Good stress corrosion cracking resistance - High strength retention - Improved fatigue performance --- #### **3. Physical Properties** | Property | Value / Description | | :--- | :--- | | **Density** | 2.82 g/cm³ (0.102 lb/in³) | | **Melting Range** | 477°C - 638°C (890°F - 1180°F) | | **Electrical Conductivity** | 34-38% IACS | | **Thermal Conductivity** | 125-145 W/m·K | | **Coefficient of Thermal Expansion** | 23.5 × 10⁻⁶/°C (20-100°C) | | **Modulus of Elasticity** | 71 GPa (10.3 × 10⁶ psi) | --- #### **4. Mechanical Properties (Typical)** | Property | T76 Temper | T7651 Temper | | :--- | :--- | :--- | | **Tensile Ultimate Strength** | 500 - 550 MPa (73 - 80 ksi) | 490 - 540 MPa (71 - 78 ksi) | | **Tensile Yield Strength (0.2% Offset)** | 440 - 490 MPa (64 - 71 ksi) | 430 - 480 MPa (62 - 70 ksi) | | **Elongation** | 7-11% | 8-12% | | **Compression Yield Strength** | 430 - 480 MPa (62 - 70 ksi) | 420 - 470 MPa (61 - 68 ksi) | | **Shear Strength** | 280 - 320 MPa (41 - 46 ksi) | 270 - 310 MPa (39 - 45 ksi) | | **Fatigue Strength** | 150 - 180 MPa (22 - 26 ksi) | 145 - 175 MPa (21 - 25 ksi) | | **Brinell Hardness** | 130 - 145 HB | 125 - 140 HB | --- #### **5. Product Applications** **7178-T76/T7651** is used in applications requiring both high strength and good corrosion resistance: * **Aerospace Structures:** * Aircraft lower wing skins * Fuselage components * Wing ribs and spars * Structural brackets * Military aircraft components * **Marine Applications:** * Marine aircraft components * Boat and ship structures * Offshore components * **Defense Applications:** * Military vehicle components * Naval aircraft structures * Defense system components * **Industrial Applications:** * High-strength structural components * Machinery parts in corrosive environments * Material handling equipment --- #### **6. International Standards** | Standard Body | Designation | Specification | | :--- | :--- | :--- | | **Aluminum Association** | 7178-T76 / 7178-T7651 | AA Teal Sheets | | **ASTM International** | 7178-T76 / 7178-T7651 | ASTM B209 | | **Aerospace (AMS)** | 7178-T76 | AMS 4096 | | **Aerospace (AMS)** | 7178-T7651 | AMS 4097 | | **European Norm** | EN AW-7178 T76 / T7651 | EN 485-2 | | **Unified Numbering System** | A97178 | UNS Registry | --- #### **7. Key Characteristics** **Advantages:** - **Excellent exfoliation corrosion resistance** - **Good stress corrosion cracking resistance** - **High strength retention** (approximately 90-95% of T6 strength) - **Good fatigue performance** - **Improved dimensional stability** (T7651) - **Suitable for marine environments** **Limitations:** - Slightly lower strength than T6 temper - Higher cost due to specialized heat treatment - Limited formability in aged condition - Requires proper handling and storage --- #### **8. Manufacturing Considerations** * **Machining:** Good machinability with proper tooling and techniques * **Forming:** Limited formability in aged condition * **Welding:** Not generally recommended for fusion welding * **Heat Treatment:** Requires precise control of aging parameters * **Surface Treatment:** Excellent for anodizing and coating applications --- #### **9. Special Features** **7178-T76/T7651** offers a unique balance of properties: * **Optimal Balance:** Better corrosion resistance than T6, higher strength than T73 * **Heat Treatment:** Controlled over-aging to achieve specific precipitation structure * **Environmental Performance:** Suitable for moderate marine and industrial environments * **Quality Assurance:** Strict control of mechanical and corrosion properties **Comparison with Other Tempers:** - **vs T6:** Better corrosion resistance with minimal strength reduction - **vs T73:** Higher strength with good corrosion resistance - **vs T7651:** Similar properties with specific application focus --- #### **10. Performance Characteristics** - **Exfoliation Corrosion:** Rating of EA to EB per ASTM G34 - **Stress Corrosion Cracking:** Good resistance in short transverse direction - **Fatigue Life:** Excellent for aircraft structural applications - **Fracture Toughness:** Maintains good damage tolerance **7178-T76/T7651 Aluminum Alloy** represents an excellent compromise for applications requiring both high strength and good corrosion resistance. The temper is particularly valuable for aerospace components exposed to marine environments and for structural applications where both mechanical performance and durability are important design considerations. The T7651 variant provides additional benefits for precision components requiring stable dimensions during machining operations.

Packing of Standard Packing: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 2199 gallon liquid totes Special package is available on request.