2021 Aluminum alloy,Aluminum 2021 alloy,E FORU

### **2021 Aluminum Alloy Product Introduction** **Overview** 2021 Aluminum Alloy is a high-strength, heat-treatable aluminum-copper alloy renowned for its exceptional elevated temperature performance. Its key distinguishing feature is the significant addition of **Zirconium (Zr)**, which forms fine, stable dispersoids that inhibit recrystallization and grain growth. This makes 2021 particularly suitable for applications requiring sustained strength and stability at temperatures higher than those typically possible with standard 2xxx series alloys like 2024 or 2017. It is commonly used in the T81 temper, which involves solution heat treatment, cold working, and artificial aging to maximize its properties. --- #### **1. Chemical Composition (Typical Weight %)** The composition of 2021 is characterized by high copper and the critical addition of zirconium. | Element | Minimum (%) | Maximum (%) | Notes | | :--- | :--- | :--- | :--- | | **Aluminum (Al)** | Balance | Balance | - | | **Copper (Cu)** | 5.8 | 6.8 | Primary strengthening element. | | **Manganese (Mn)** | 0.20 | 0.40 | Improves strength and grain structure control. | | **Zirconium (Zr)** | 0.15 | 0.25 | **Key element** that provides thermal stability by inhibiting grain growth at high temperatures. | | **Titanium (Ti)** | 0.02 | 0.10 | Acts as a grain refiner. | | **Silicon (Si)** | - | 0.20 | Impurity. | | **Iron (Fe)** | - | 0.30 | Impurity. | | **Zinc (Zn)** | - | 0.10 | Impurity. | | **Others (Each)** | - | 0.05 | - | | **Others (Total)** | - | 0.15 | - | **Key Point:** The high copper content and the deliberate addition of Zirconium are what set 2021 apart. Zirconium forms coherent Al₃Zr precipitates that pin grain boundaries, providing exceptional resistance to softening over time at elevated temperatures. --- #### **2. Physical Properties** | Property | Value / Description | | :--- | :--- | | **Density** | 2.83 g/cm³ (0.102 lb/in³) | | **Melting Range** | ~ 540°C - 650°C ( ~1000°F - 1200°F) | | **Electrical Conductivity** | ~ 30-35% IACS (International Annealed Copper Standard) | | **Thermal Conductivity** | ~ 120-130 W/m·K (at 25°C) | | **Coefficient of Thermal Expansion** | ~ 23.2 x 10⁻⁶/°C (20-100°C) | --- #### **3. Mechanical Properties (Typical for T81 Temper)** The T81 temper (solution heat-treated, cold worked, and then artificially aged) is the standard condition for achieving high strength and thermal stability. | Temper | Tensile Strength | Yield Strength (0.2% Offset) | Elongation (% in 50mm) | | :--- | :--- | :--- | :--- | | **2021-T81** | min. 455 MPa (66 ksi) | min. 395 MPa (57 ksi) | min. 6% | *Note: The key advantage of 2021-T81 is its ability to retain a significant portion of this strength after prolonged exposure to elevated temperatures (e.g., 150-200°C / 300-400°F).* --- #### **4. International Standards** 2021 Aluminum Alloy is specified in several aerospace and general standards. | Standard System | Alloy Designation | Common Tempers | | :--- | :--- | :--- | | **ASTM (USA)** | **2021** | T81 | | **AMS (Aerospace)** | **AMS 4202** | T81 (Sheet and Plate) | | **UNS (USA)** | **A92021** | - | --- #### **5. Product Applications** 2021 is a specialized alloy primarily used in high-performance aerospace applications where temperature resistance is critical. * **Aerospace & Supersonic Aviation:** * **Supersonic Aircraft Skin and Structural Members:** Its ability to retain strength at the aerodynamic heating temperatures encountered during sustained high-speed flight is its primary application. * **Rocket and Missile Components:** Used for casings, bulkheads, and other structures that experience moderate heating. * **Engine Cowlings and Accessories:** For parts close to engine heat sources. * **High-Temperature Fasteners.** --- #### **6. Key Advantages & Considerations** * **Advantages:** * **Excellent Elevated Temperature Strength:** Superior retention of mechanical properties after prolonged exposure to temperatures up to ~200°C (400°F) compared to most other aluminum alloys. * **High Strength-to-Weight Ratio:** At elevated temperatures, it outperforms many competing Al-alloys. * **Good Stress-Corrosion Cracking Resistance:** The T8 temper (which includes artificial aging) generally imparts better resistance to stress-corrosion cracking compared to the T4 temper in other Al-Cu alloys. * **Considerations:** * **Poor Corrosion Resistance:** Like all high-copper aluminum alloys, it has very poor resistance to general corrosion, particularly in saltwater environments. It requires protective coatings such as **Alclad** (for sheet) or anodizing. * **Limited Formability:** In the T81 temper, it has low ductility and is not suitable for severe forming operations. Forming is typically done in the annealed ("O") condition before final heat treatment. * **Not Weldable:** It is generally considered non-weldable by common fusion welding techniques due to its high susceptibility to solidification cracking and loss of properties. * **Specialized and Costly:** It is a niche, premium-priced alloy compared to more common grades like 2024 or 7075. **Conclusion** 2021-T81 Aluminum Alloy is a highly specialized material engineered for one of the most demanding environments for aluminum: sustained high temperature. While it shares the corrosion and welding challenges of the 2xxx series, its unique composition with Zirconium provides a critical performance advantage in supersonic aerospace and missile applications. It serves as a material solution where the lightweight properties of aluminum are needed, but the thermal environment is too severe for other aluminum alloys.

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 1528 gallon liquid totes Special package is available on request.