1. Introduction
2024 aluminum alloy stands out as one of the most versatile heat‐treatable alloys in modern engineering.
By combining high strength with good fatigue resistance, it serves critical roles in aerospace, defense, and high‐performance applications.
Developed in the 1940s, 2024 quickly became the alloy of choice for aircraft wing skins, fuselage frames, and structural components.
In this article, we examine the mechanical performance, metallurgical behavior, corrosion resistance, fabrication processes, and real-world applications of 2024 aluminum.
2. Chemical Composition of 2024 Aluminum
2024 aluminum alloy belongs to the Al–Cu–Mg–Mn family, where each element plays a precise metallurgical role. Its typical composition breaks down as follows:
| Element | Typical Range (wt %) | Function |
|---|---|---|
| Copper (Cu) | 3.8 – 4.9 | Primary strengthening element via Al₂Cu precipitates |
| Magnesium (Mg) | 1.2 – 1.8 | Enhances precipitation hardening and overall strength |
| Manganese (Mn) | 0.30 – 0.90 | Grain‐refinement dispersoid former; improves toughness |
| Iron (Fe) | ≤ 0.50 | Kept low to minimize brittle intermetallic formation |
| Silicon (Si) | ≤ 0.50 | Controls casting fluidity; low levels avoid coarse phases |
| Zinc (Zn) | ≤ 0.25 | Trace addition; can slightly boost strength |
| Chromium (Cr) | 0.10 – 0.25 | Hinders recrystallization; improves corrosion resistance |
| Titanium (Ti) | ≤ 0.15 | Refines grain structure; promotes uniform microstructure |
| Others (Cu, Mg, Mn, etc.) | Balance (Al) | Aluminum constitutes the remainder, ensuring low density and good formability |
3. Key Variants and Heat Treatments
- 2024-T3: Solution‐treated, cold‐worked, and naturally aged. Offers UTS ≈ 470 MPa and YS ≈ 325 MPa.
- 2024-T351: Similar to T3 but with stress‐relief stretching, improving dimensional stability for sheet and plate.
- 2024-T4: Solution‐treated and naturally aged; UTS drops to ≈ 435 MPa but retains better formability.
- 2024-T851: Solution‐treated, stress‐relieved, and artificially aged; balances strength (UTS ≈ 460 MPa) with excellent resistance to exfoliation corrosion.
4. Physical and Mechanical Properties of 2024 Aluminum
2024 aluminum delivers an exceptional balance of lightweight, thermal performance, and high strength.
Physical Properties of 2024 Aluminum
| Property | Value |
|---|---|
| Density | 2.78 g/cm³ |
| Thermal Conductivity | ~120 W/m·K |
| Coefficient of Thermal Expansion | 23.2 × 10⁻⁶ /°C |
| Specific Heat | 880 J/kg·K |
| Elastic Modulus | 73 GPa |
| Operating Temperature Limit | ≤ 150 °C (short term ≈ 180 °C) |
Room-Temperature Mechanical Properties
| Property | 2024-T3 | 2024-T4 | 2024-T351 | 2024-T851 |
|---|---|---|---|---|
| Ultimate Tensile Strength (MPa) | 483 | 469 | 483 | ≥ 455 |
| Yield Strength (0.2 % offset, MPa) | 345 | 324 | 345 | ≥ 400 |
| Modulus of Elasticity (GPa) | 73.1 | 73.1 | 73.1 | 72.4 |
| Brinell Hardness (HB) | 120 | 120 | 120 | 128 |
| Elongation at Break (%) | 18 % | 19 % | 18 % | 5 % |
| Shear Modulus (GPa) | 28 | 28 | 28 | 27 |
| Shear Strength (MPa) | 283 | 283 | 283 | 296 |
| Fatigue Strength (MPa) | 138 | 138 | 138 | 117 |
Fatigue Performance and Crack-Growth Behavior
Under fully reversed bending (R = –1), 2024-T3 exhibits an endurance limit of approximately 160 MPa at 10⁷ cycles.
Its fatigue crack-growth rate follows a Paris law exponent of 3.0–3.5, indicating moderate sensitivity to stress-intensity range.
Shot-peening or cold-working near the surface can raise the fatigue limit by 10–20%, making 2024 suitable for cyclically loaded aircraft skins and rotating structures.
High-Temperature Stability and Creep Resistance
Although 2024 retains more than 90% of its T3 strength after a 100 °C exposure for 100 hours, it begins to soften above 120–150 °C.
At 150 °C, creep rates become measurable under sustained loads—limiting long-term service to below 130 °C.
Engineers therefore reserve 2024 for ambient-to-moderate temperature applications, while selecting other alloys (e.g., 6061 or 7075) or stainless steels for hotter service.
5. Corrosion Behavior and Surface Protection
Although 2024 resists general corrosion in dry air, it suffers from pitting and intergranular attack in marine or acidic conditions.
The alloy’s high copper content concentrates at grain boundaries during aging, creating sites for localized corrosion. To mitigate this risk, engineers apply:
- Anodizing: Produces a 10–20 µm thick Al₂O₃ layer, enhancing barrier protection and allowing dyeing for identification.
- Cladding (Alclad): Bonding a thin layer (5–10%) of pure aluminum to 2024 sheet dramatically improves corrosion resistance in aerospace skins.
- Conversion Coatings: Chromate or non‐chromate sprays passivate the surface before primer and paint.
6. Fabrication and Machinability of 2024 Aluminum Alloy
2024 aluminum alloy’s utility in high-stress applications hinges on its adaptability to diverse fabrication processes,
though its performance requires careful control of forming, heat treatment, and machining parameters.
Forming and Forging Characteristics
Cold Forming Behavior
- Temper-Dependent Ductility:
-
- In T3/T4/T351 tempers, the alloy exhibits excellent cold formability due to moderate strength (tensile strength ~470–525 MPa) and high elongation (10–12%).
It readily undergoes stamping, bending, roll forming, and stretch forming, making it ideal for complex aerospace components like wing skins or fuselage panels. - T851 temper, however, is significantly less formable (elongation 6–8%) due to increased hardness from artificial aging.
Cold working in this state risks cracking and requires preheating to 100–150°C to improve ductility.
- In T3/T4/T351 tempers, the alloy exhibits excellent cold formability due to moderate strength (tensile strength ~470–525 MPa) and high elongation (10–12%).
- Work-Hardening Rate: 2024 alloy exhibits a moderate work-hardening exponent (n ≈ 0.15–0.20), meaning it stiffens gradually during deformation.
Intermediate annealing (300–350°C for 1–2 hours) may be necessary for multi-stage forming to restore ductility and reduce internal stresses.
Hot Forming and Forging
- Forging Temperature Range: Optimal forging occurs at 350–450°C, where the alloy’s flow stress decreases (≈50–100 MPa) and grain growth is minimized.
Preheating dies to 200–250°C reduces thermal shock and improves material flow. - Microstructural Control: Post-forging cooling rates must be controlled to avoid coarse grain formation.
Rapid air cooling is typical for most applications, while slower cooling may require subsequent homogenization (490–520°C for 4–8 hours) to dissolve residual segregation and improve mechanical uniformity. - Application Example: High-strength aerospace forgings (e.g., landing gear components) often use T851-tempered 2024,
with forging processes optimized to align grain flow along stress paths, enhancing fatigue resistance.
Machinability
2024 aluminum alloy is rated fair to good in machinability (machinability index ≈ 40–50, where 100 = free-cutting brass), with performance influenced by temper, tooling, and cutting parameters.
Key Challenges
- Work-Hardening During Cutting: The alloy tends to work-harden at the cutting edge, especially in T851 temper, leading to tool wear if feeds and speeds are suboptimal.
- Chip Welding (Built-Up Edge): Soft, ductile matrix in T3/T4 tempers can adhere to tool surfaces, causing surface roughness and tool failure.
- Thermal Sensitivity: High copper content increases thermal conductivity (121 W/m·K), but concentrated heat at the cutting zone can still degrade tool life if coolant is insufficient.
Surface Finish
- Properly tuned parameters can achieve Ra ≤ 1.6 μm in T3/T4 tempers, while T851 may require finer feeds (≤0.15 mm/rev) to match this finish due to its higher hardness.
Post-Fabrication Heat Treatment and Stress Relief
- Formed Components: Parts shaped in T3/T4 tempers often undergo stabilization annealing (120–150°C for 24–48 hours) to reduce residual stresses and prevent stress-corrosion cracking in service.
- Forged Parts: After forging and machining, T851-tempered components require solution heat treatment (495–505°C for 1–2 hours),
quenching, and artificial aging (190°C for 12–16 hours) to achieve peak strength.
7. Is 2024 Aluminum Good for Welding?
Welding 2024 poses challenges. Its high copper content reduces weld‐zone strength and increases hot‐cracking risk.
Gas‐tungsten (GTAW) or gas‐metal arc welding (GMAW) with 2319 or 4043 filler alloys can join 2024,
but designers typically avoid structural welds in favor of mechanical fastening or adhesive bonding.
When necessary, preheating to 100 °C and post‐weld artificial aging (T8x temper) help restore up to 80% of base‐metal strength.
8. Applications of 2024 Aluminum Alloy
The 2024 aluminum alloy stands out as one of the most widely used high-strength materials in aerospace and transportation sectors
due to its exceptional fatigue resistance, moderate formability, and high strength-to-weight ratio.
Aerospace Industry
2024-T3 and T351 are staples in aircraft manufacturing, particularly for:
- Wing Skins & Fuselage Structures: High fatigue resistance and good formability make 2024 ideal for large, thin-walled sections such as wing skins, fuselage frames, and ribs.
- Bulkheads and Stringers: Components that require high strength and resistance to cyclic loading over long service lives.
- Landing Gear Forgings (T851): The T851 temper, with its excellent strength and stress-corrosion resistance, is employed in forged parts such as landing gear beams, actuators, and hinges.
Automotive and Motorsport
Although not as widely used in mass-production vehicles due to corrosion sensitivity, 2024 finds niche use in:
- Motorsport Chassis and Suspension Arms: Where maximum strength-to-weight ratio is essential for speed and maneuverability.
- Custom Performance Parts: Racing-grade wheels, strut bars, and cross members.
Industrial and Structural Equipment
2024 alloy is applied in high-load, fatigue-prone industrial components, including:
- Hydraulic and Pneumatic Fittings
- Load-Bearing Connectors and Fasteners
- Bridge Components and Mechanical Linkages
Its use is typically restricted to applications where surface protection (via cladding or coatings) can mitigate corrosion exposure.
Other Specialty Uses
- Robotics and Automation Systems: Lightweight structural arms and end-effectors in high-speed robotic assemblies.
- High-Performance Bicycles and Sporting Goods: Frames and critical joints in racing bikes, particularly where dynamic loads are intense.
9. Pros and Cons of 2024 Aluminum Alloy
2024 aluminum alloy, particularly in its heat-treated forms (T3, T4, T351, T851),
offers a well-balanced combination of high strength and fatigue resistance, making it a material of choice for structural applications.
Pros of 2024 Aluminum
High Strength-to-Weight Ratio
- Among the strongest of the aluminum alloys, especially in T3 and T851 tempers, with tensile strengths reaching 470–505 MPa.
- Enables significant weight savings in aerospace and transportation applications.
Excellent Fatigue Resistance
- Superior to many other aluminum grades under cyclic loading conditions.
- Ideal for components subjected to repeated stress, such as aircraft wings and automotive suspension systems.
Good Machinability
- Rated fair to good, particularly in the T3 and T4 tempers.
- Produces consistent chip formation and allows for tight tolerances with appropriate tooling.
Moderate Formability in Annealed or T3/T4 Conditions
- Can be stretch-formed, roll-formed, and stamped with good accuracy.
- Useful for complex aerodynamic shapes in aircraft skins and frames.
Enhanced Properties Through Heat Treatment
- Wide range of tempers allows designers to tailor strength, ductility, and corrosion resistance.
- Artificial aging (T851) improves mechanical performance for heavy-duty applications.
Proven Aerospace Legacy
- Decades of successful use in critical aerospace structures validate its performance and reliability.
Cons of 2024 Aluminum
Poor Corrosion Resistance
- Especially vulnerable to intergranular and pitting corrosion in marine and moist environments.
- Requires protective cladding, anodizing, or conversion coatings for long-term durability.
Limited Weldability
- Not recommended for fusion welding due to hot cracking and loss of mechanical properties in the heat-affected zone.
- Mechanical fastening or friction stir welding is preferred.
Lower Workability in High-Strength Tempers
- Tempers like T851 exhibit reduced ductility and higher risk of cracking during cold forming.
- May require preheating or intermediate annealing.
Thermal Sensitivity During Machining
- High copper content leads to rapid heat buildup at cutting edges, which can degrade tool life without adequate cooling.
Susceptibility to Stress Corrosion Cracking (SCC)
- Components under sustained tensile stress in corrosive environments may experience SCC unless properly stress-relieved.
Cost Relative to Common Alloys
- More expensive than 6061 or 5052 aluminum due to its copper alloying and heat treatment requirements.
10. Comparison with Other Al–Cu Alloys and Competitors
2024 aluminum alloy is widely regarded for its strength and fatigue resistance, but it does not exist in isolation.
Comparison Table: 2024 Aluminum vs. Competing Materials
| Property | 2024 Aluminum | 7075 Aluminum | 6061 Aluminum | Ti-6Al-4V (Titanium) | Carbon Fiber Composite |
|---|---|---|---|---|---|
| Density (g/cm³) | 2.78 | 2.81 | 2.70 | 4.43 | ~1.6 |
| Tensile Strength (MPa) | 470–505 (T3/T851) | 540–580 (T6) | 310–350 (T6) | 900–1000 | 600–1300 (fiber direction) |
| Fatigue Resistance | Excellent | Very Good | Moderate | Excellent | Excellent (anisotropic) |
| Corrosion Resistance | Moderate to Poor | Fair to Moderate | Good | Excellent | Excellent |
| Weldability | Poor | Very Poor | Excellent | Moderate (with shielding) | Poor |
| Machinability | Fair to Good | Fair | Excellent | Moderate | Poor (abrasive) |
| Formability | Good (T3/T4) | Poor | Very Good | Moderate (hot forming) | Limited |
| Cost | Moderate | Higher | Low | Very High | Very High |
| Typical Applications | Aerospace skins, frames | Aircraft spars, defense | General structural use | Jet engines, implants | Aerospace, sports, EVs |
11. Conclusion
2024 aluminum alloy combines high strength, fatigue endurance, and lightweight construction, making it indispensable in aerospace and defense.
Yet its vulnerability to corrosion and limited weldability demand protective coatings and alternative joining methods.
Engineers must weigh these trade‐offs against cost and performance requirements.
As next‐generation Al–Cu–Mg alloys and additive manufacturing advance,
developers will refine 2024 aluminum’s pedigree—potentially boosting its service temperature, corrosion resistance, and processability for future high‐performance applications.
LangHe delivers reliable, high-quality aluminum alloy components that meet stringent international standards.
Contact us today to discuss your next project.
FAQs
What is 2024 grade aluminum?
2024 aluminum is a high-strength, heat-treatable wrought alloy in the Al–Cu–Mg–Mn family. It typically contains 3.8–4.9 % Cu, 1.2–1.8 % Mg and 0.3–0.9 % Mn, with the balance Al.
In T3 or T351 tempers, it delivers ultimate tensile strengths around 470–505 MPa and excellent fatigue resistance,
making it a mainstay for aerospace skins, fuselage frames, and other structural components.
Is 2024 aluminum stronger than 6061?
Yes. In equivalent tempers (e.g. T6 for 6061 and T3 for 2024), 2024’s tensile strength (~470 MPa) significantly exceeds 6061-T6’s (~310 MPa).
However, 6061 offers better corrosion resistance, weldability, and formability, so engineers choose between them based on whether maximum strength or ease of processing is paramount.
What is the 2024 aluminum aircraft?
Many commercial and military aircraft incorporate 2024 alloy in critical load-bearing panels.
For example, Boeing 737 and Airbus A320 series use 2024-T3/T351 for wing skins, fuselage frames, and bulkheads.
Fighter jets (e.g., F-16) also employ 2024 in structural ribs and access panels where fatigue life is crucial.
What is the difference between 2024 and 7075 aluminum?
- Composition: 2024 is an Al–Cu–Mg–Mn alloy (≈4 % Cu), whereas 7075 is an Al–Zn–Mg–Cu alloy (≈5–6 % Zn).
- Strength: 7075-T6 reaches ~540–580 MPa UTS, higher than 2024-T3’s ~470 MPa.
- Fatigue & Toughness: 2024 typically shows better fracture toughness and fatigue crack-growth resistance.
- Corrosion & Weldability: Neither welds well, but 7075 is more prone to exfoliation corrosion; 2024 often receives Alclad or coatings.
- Formability: 2024 (T3/T4) forms more readily than 7075, which tends to crack during bending.
