Aluminum 2024
Introduction to Aluminum 2024
Aluminum 2024 is a high-strength, heat-treatable aluminum alloy primarily alloyed with copper, making it ideal for structural applications requiring superior fatigue resistance and load-bearing capacity. Although less corrosion-resistant than 6xxx series alloys, it offers unmatched strength-to-weight performance in dry and controlled environments.
With excellent machinability in its heat-treated T4 or T351 tempers, Aluminum 2024 is widely used in CNC machining for aerospace, military, automotive, and precision tooling applications where high static and cyclic strength is essential.
Chemical, Physical, and Mechanical Properties of Aluminum 2024
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Aluminum (Al) | Balance | Lightweight base with moderate corrosion resistance |
Copper (Cu) | 3.8–4.9 | Primary strengthening agent via precipitation hardening |
Magnesium (Mg) | 1.2–1.8 | Enhances strength and fatigue resistance |
Manganese (Mn) | 0.3–0.9 | Improves corrosion resistance and toughness |
Silicon (Si) | ≤0.5 | Residual element |
Iron (Fe) | ≤0.5 | Residual element |
Zinc (Zn) | ≤0.25 | Residual element |
Titanium (Ti) | ≤0.15 | Grain refining agent |
Chromium (Cr) | ≤0.10 | Improves stress-corrosion resistance |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 2.78 g/cm³ | ASTM B311 |
Melting Point | 502–638°C | ASTM E299 |
Thermal Conductivity | 121 W/m·K at 25°C | ASTM E1952 |
Electrical Conductivity | 30% IACS at 20°C | ASTM B193 |
Coefficient of Expansion | 22.8 µm/m·°C | ASTM E228 |
Specific Heat Capacity | 875 J/kg·K | ASTM E1269 |
Elastic Modulus | 73.1 GPa | ASTM E111 |
Mechanical Properties (T4/T351 Temper)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 470 MPa (T351) | ASTM E8/E8M |
Yield Strength (0.2%) | 325 MPa (T351) | ASTM E8/E8M |
Elongation | ≥10% | ASTM E8/E8M |
Hardness | 120 HB | ASTM E10 |
Fatigue Strength | 138 MPa | ASTM E466 |
Impact Resistance | High | ASTM E23 |
Key Characteristics of Aluminum 2024
Superior Strength and Fatigue Resistance: 2024 is one of the strongest aluminum alloys available for CNC machining, delivering a tensile strength of 470 MPa and a fatigue limit of 138 MPa—ideal for aircraft, suspension, and cyclic-load parts.
Excellent Machinability: 2024 in T351 condition offers crisp chip control and reduced tool wear when machined with high-speed steel or coated carbide tools, supporting tolerances of ±0.005 mm.
Lower Corrosion Resistance: While 2024 lacks inherent corrosion protection, it performs reliably in dry, low-moisture environments or with proper surface treatments like anodizing or alodine coating.
High Thermal Conductivity: Its conductivity (121 W/m·K) enables rapid heat dissipation, beneficial for components in friction-intensive or thermal-sensitive systems.
Dimensional Stability and Strength Retention: 2024 retains dimensional accuracy under machining stress and maintains strength up to 125°C, common in aerospace assemblies.
CNC Machining Challenges and Solutions for Aluminum 2024
Machining Challenges
Corrosion Sensitivity: Requires protective coatings or controlled environments.
High Copper Content: Increases tool wear and requires proper chip removal.
Risk of Surface Pitting: Particularly if inadequate cooling or dull tools are used.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | TiAlN- or TiB₂-coated carbide | Resists adhesive wear and maintains sharp edge |
Geometry | High rake angle with polished flutes | Supports chip evacuation and surface integrity |
Cutting Speed | 150–400 m/min | Prevents BUE and thermal damage |
Feed Rate | 0.10–0.25 mm/rev | Controls chip load and finish |
Coolant | Mist or flood coolant | Reduces oxidation and improves tool life |
Aluminum 2024 Cutting Parameters (ISO 513 Compliance)
Operation | Speed (m/min) | Feed (mm/rev) | Depth of Cut (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 150–250 | 0.15–0.25 | 2.0–3.5 | 20–30 (Flood) |
Finishing | 300–400 | 0.05–0.15 | 0.2–1.0 | 30–50 (Mist/Flood) |
Surface Treatment for Aluminum 2024 CNC Parts
Anodizing: Best applied after cladding; Type II for basic protection, Type III (up to 50 µm) for added wear resistance.
Powder Coating: A durable 60–120 µm finish enhances UV resistance and impact strength for external or visible assemblies.
Electropolishing: Smooths high-tolerance parts and increases fatigue resistance, particularly beneficial in rotating hardware.
Passivation: Removing residual contaminants helps prepare the surface for painting or powder coating.
Brushing: Ideal for functional or semi-cosmetic finishes with Ra values between 0.8–1.6 µm.
Alodine Coating: MIL-DTL-5541-compliant surface treatment commonly used for aerospace electronics and bonded assemblies.
UV Coating: Adds protective film for consumer electronics and lightweight enclosures prone to handling.
Lacquer Coating: Protects decorative components while maintaining the dimensional accuracy of machined geometries.
Industry Applications of Aluminum 2024
Aerospace: Fuselage skins, bulkheads, riveted frames, and wing stiffeners requiring fatigue strength.
Defense: Armor plates, drone structural frames, and ballistic enclosures where strength is critical.
Automotive: Racing suspension systems, drivetrain components, and crash-resistant reinforcements.
Tooling & Molds: Base plates, jigs, and fixtures where stability and wear resistance are key.
Robotics: Lightweight joints, brackets, and end effectors requiring high stiffness under motion.
FAQs
What makes Aluminum 2024 preferable for aerospace CNC components?
How does Aluminum 2024 compare to 6061-T6 regarding strength and corrosion resistance?
What are the best surface treatments for protecting 2024 in marine or humid environments?
Can Aluminum 2024 be welded, or does mechanical joining be required?
What machining considerations are unique to 2024-T351 alloy?
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