2024 Aluminum Alloy Introduction
2024 aluminum alloy is a high-strength, heat-treatable member of the 2000 series aluminum alloys (Al-Cu-Mg-Mn system), renowned for its excellent strength-to-weight ratio and superior fatigue resistance. It is one of the most widely used structural alloys in aerospace, aviation, and high-performance engineering applications. Below is a comprehensive overview:
I. Basic Information
Alloy Series: 2000 series (Aluminum-Copper-Magnesium-Manganese alloy)
Key Feature: A “workhorse” alloy in aerospace due to its balance of strength, toughness, and fatigue performance.
Standards: Conforms to international standards such as ASTM B209 (wrought aluminum sheets and plates), ASTM B211 (bars, rods, wires), and EN 485-2 (European standard for wrought aluminum alloys for structural applications).
II. Chemical Composition (Mass Fraction, %)
The composition of 2024 aluminum alloy is optimized to achieve high strength and structural stability:
Element Content Range Element Content Range
Aluminum (Al) Remainder Copper (Cu) 3.8% – 4.9%
Magnesium (Mg) 1.2% – 1.8% Manganese (Mn) 0.3% – 0.9%
Iron (Fe) ≤0.5% Silicon (Si) ≤0.5%
Zinc (Zn) ≤0.25% Titanium (Ti) ≤0.15%
Other Impurities Each ≤0.05%, Total ≤0.15% – –
Note: Copper and magnesium form strengthening phases (e.g., Al₂CuMg) during heat treatment, while manganese improves corrosion resistance and controls grain structure.
III. Core Properties
1. Mechanical Properties (Typical Values, After Heat Treatment)
Tensile Strength: 440 – 480 MPa (T6 temper)
Yield Strength: 325 – 380 MPa (T6 temper)
Elongation (δ5): 10% – 15% (T6 temper, indicating good ductility for forming)
Hardness (HB): 120 – 140 (T6 temper, providing strong wear resistance)
Fatigue Strength: ~140 MPa (at 10⁷ cycles, critical for dynamic load applications)
Temper Notes: T6 (solution heat-treated and artificially aged) is the most common temper for 2024, balancing strength and toughness.
2. Key Characteristics
High Strength: Among the strongest 2000 series alloys, suitable for structural components under heavy loads.
Excellent Fatigue Resistance: Performs well under repeated stress, making it ideal for parts like aircraft wings or landing gear components.
Good Formability: Can be cold-worked (e.g., bending, rolling) in the annealed state (O temper) and retains formability after partial heat treatment.
Heat-Treatable: Strengthened via solution annealing (495 – 505°C, water-quenched) followed by artificial aging (120 – 190°C), which precipitates fine Cu-Mg phases to enhance strength.
Corrosion Resistance: Moderate in normal environments but prone to intergranular corrosion if improperly heat-treated. Often clad with pure aluminum (e.g., 2024-0 clad) or treated with anodizing to improve corrosion resistance.
Weldability: Limited weldability due to high copper content (risk of hot cracking). Welding is possible with TIG/MIG using 4043 filler metal but may require post-weld heat treatment to restore strength.
IV. Processing & Surface Treatment
Forming: Easily cold-formed in the O temper; hot forming is possible for complex shapes.
Machining: Good machinability in the T6 temper, though less efficient than free-machining alloys like 2011.
Surface Treatment: Anodizing (Type II or III) improves corrosion resistance and wear; chemical conversion coatings (e.g., chromate, zirconium) are used for pre-paint adhesion.
V. Applications
Aerospace: Aircraft structural parts (wings, fuselages), landing gear components, and fasteners (leveraging high strength and fatigue resistance).
Automotive: High-performance racing parts, suspension components, and precision machined parts.
Industrial: Tooling, molds, and structural brackets requiring a balance of strength and formability.
Summary
2024 aluminum alloy is prized for its high strength, fatigue resistance, and formability, making it a staple in aerospace and high-performance engineering. While its corrosion resistance and weldability are limited, strategic use of cladding, surface treatments, and careful processing ensure its reliability in demanding applications.