7278 Aluminum alloy,Aluminum 7278 alloy，E FORU

### **Introduction to 7278 Aluminum Alloy** **Aluminum 7278** is a high-strength, heat-treatable wrought alloy belonging to the **Al-Zn-Mg-Cu (7xxx series)** family. It is renowned for its exceptional combination of very high strength, good fracture toughness, and excellent stress corrosion cracking (SCC) resistance. This alloy is primarily used in aerospace and other high-performance applications where the strength-to-weight ratio is a critical design parameter. While not as universally common as the widely used 7075 or 2024 alloys, 7278 is specified for applications demanding the ultimate strength achievable with aluminum. --- ### **1. Chemical Composition** The composition of 7278 Aluminum is tightly controlled to achieve its superior properties. The following table outlines its typical chemical composition based on international standards. | Element | Content (% by Weight) | | :--- | :--- | | **Aluminum (Al)** | Balance | | **Zinc (Zn)** | 5.2 - 6.2 | | **Magnesium (Mg)** | 2.0 - 2.8 | | **Copper (Cu)** | 1.8 - 2.4 | | **Chromium (Cr)** | 0.18 - 0.28 | | **Iron (Fe)** | ≤ 0.15 | | **Silicon (Si)** | ≤ 0.10 | | **Manganese (Mn)** | ≤ 0.05 | | **Titanium (Ti)** | ≤ 0.05 | | **Other Impurities** | ≤ 0.05 each; ≤ 0.15 total | *The high Zinc and Magnesium content, combined with significant Copper, enables the formation of strengthening precipitates during heat treatment.* --- ### **2. Physical Properties** The physical properties of 7278 Aluminum alloy are typical for high-strength aluminum alloys. | Property | Metric Value | Imperial Value | | :--- | :--- | :--- | | **Density** | 2.85 g/cm³ | 0.103 lb/in³ | | **Melting Range** | ~ 477 - 635 °C | ~ 890 - 1175 °F | | **Electrical Conductivity** | ~ 30-35% IACS | - | | **Thermal Conductivity** | ~ 130 W/m·K | - | | **Modulus of Elasticity** | 71 GPa | 10.3 x 10⁶ psi | --- ### **3. Mechanical Properties** Mechanical properties are highly dependent on the temper (heat treatment condition). The T6 temper is the most common for achieving peak strength. **Typical Room Temperature Mechanical Properties (Sheet/Plate - T651 Temper)** | Property | Value (Metric) | Value (Imperial) | | :--- | :--- | :--- | | **Tensile Ultimate Strength** | 620 - 655 MPa | 90 - 95 ksi | | **Tensile Yield Strength (0.2% Offset)** | 570 - 600 MPa | 83 - 87 ksi | | **Elongation at Break** | 7 - 10% | 7 - 10% | | **Hardness (Brinell)** | ~ 165 HB | ~ 165 HB | *Note: The T76 or T73 tempers are over-aged tempers that significantly improve resistance to exfoliation corrosion and stress corrosion cracking, albeit with a slight sacrifice (typically 10-15%) in ultimate and yield strength.* --- ### **4. International Standards** Aluminum 7278 is covered by several international standards, which define its composition, temper, and product forms. Key standards include: * **ASTM International:** * **ASTM B209:** Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate. This is the primary standard for 7278 plate and sheet products. * **Aerospace Material Specifications (AMS):** * **AMS 4203:** Covers Aluminum Alloy 7278 Plate and Sheet (solution heat treated, stretched, and artificially aged - T651/T6511 temper). * **Other National Standards:** Equivalent standards exist in other national systems (e.g., EN in Europe, GB in China), often under a different numerical designation but with a similar composition. --- ### **5. Product Applications** Due to its premium properties, 7278 is used in highly demanding structural applications, primarily in: * **Aerospace & Defense:** * Aircraft upper wing skins and structural components * Fuselage frames and bulkheads * Military aircraft landing gear parts (forgings) * Other critical airframe structures where maximum strength is required. * **High-Performance Sporting Goods:** * Bicycle frames and components for competitive racing * Baseball/Softball bats * Mountaineering equipment * **Other Industrial Applications:** * Critical components in machinery and equipment subject to high static and dynamic loads. --- ### **6. Key Characteristics & Advantages** * **Very High Strength:** Offers one of the highest strength levels among commercially available aluminum alloys. * **Excellent Strength-to-Weight Ratio:** Ideal for weight-critical applications. * **Good Fatigue Performance:** Resists cracking under cyclic loading. * **Good Fracture Toughness:** Ability to withstand cracks without catastrophic failure. * **Machinability:** Good machinability in the T6 temper. ### **Considerations** * **Corrosion Resistance:** Like other high-strength 7xxx alloys, it is not as corrosion-resistant as other series (e.g., 5xxx or 6xxx) without protective coatings or specific over-aged tempers (T7x). * **Weldability:** Generally considered poor for fusion welding due to susceptibility to solidification cracking; components are typically joined mechanically (rivets, bolts). * **Cost:** Generally more expensive than standard aerospace alloys like 7075 due to its specialized composition and processing. ### **Conclusion** Aluminum 7278 alloy represents the pinnacle of strength in traditional aluminum metallurgy. Its carefully balanced chemistry and advanced heat treatment make it the material of choice for the most structurally demanding applications in aerospace and high-performance engineering, where every gram of weight saved without compromising strength is of paramount importance.

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 2208 gallon liquid totes Special package is available on request.