2024 aluminum alloy, often referred to as “aviation aluminum,” has earned its reputation through decades of proven performance in the most demanding aerospace applications. This heat-treatable alloy, part of the Al-Cu-Mg system, offers an exceptional strength-to-weight ratio that makes it indispensable for aircraft structures, military equipment, and high-performance CNC machined components. At Dongguan Stirling Metal Products Co., Ltd., we have extensive experience machining this challenging yet rewarding material, and we will explore its technical characteristics in depth.
1. 2024 Basic Information
2024 aluminum alloy is a high-strength, precipitation-hardenable alloy developed in the 1930s and still widely used today. Its density of 2.78 g/cm³ is slightly higher than pure aluminum (2.70 g/cm³) due to copper and magnesium additions, but it achieves tensile strengths exceeding 470 MPa in the T6 temper. The alloy is classified under the 2xxx series (Al-Cu) and is known for excellent machinability, good fatigue resistance, and moderate corrosion resistance that can be enhanced through cladding or anodizing. Key tempers include T3 (solution heat-treated, cold-worked, and naturally aged), T4 (solution heat-treated and naturally aged), T6 (solution heat-treated and artificially aged), and T351 (stress-relieved by stretching). The alloy’s unique combination of properties stems from its precipitation hardening mechanism: during aging, CuAl₂ (θ phase) and Al₂CuMg (S phase) precipitates form, creating a dense network of obstacles that impede dislocation movement, thereby increasing strength. The typical grain size after solution treatment ranges from 20 to 50 µm, which contributes to its excellent fatigue performance under cyclic loading conditions.
2. Chemical Composition
The precise chemical composition of 2024 aluminum alloy is critical to its mechanical properties. The following table provides the standard composition ranges per ASTM B209 and EN 573-3 specifications:
| Element | Content Range (%) | Role in Alloy |
|---|---|---|
| Aluminum (Al) | Balance (90.7–94.7) | Base metal, lightweight matrix |
| Copper (Cu) | 3.8–4.9 | Primary strengthening element via precipitation hardening |
| Magnesium (Mg) | 1.2–1.8 | Enhances strength through solid solution and precipitation |
| Manganese (Mn) | 0.3–0.9 | Improves corrosion resistance and grain structure |
| Silicon (Si) | ≤0.50 | Impurity, controlled to avoid embrittlement |
| Iron (Fe) | ≤0.50 | Impurity, reduces ductility if excessive |
| Zinc (Zn) | ≤0.25 | Minor strengthening effect |
| Titanium (Ti) | ≤0.15 | Grain refiner during casting |
| Chromium (Cr) | ≤0.10 | Controls grain growth |
| Others (each) | ≤0.05 | Trace elements |
| Others (total) | ≤0.15 | Sum of all trace elements |
Note: The copper content is the key differentiator from other 2xxx alloys like 2017 or 2025. Higher copper (up to 4.9%) gives 2024 its superior strength but reduces weldability and corrosion resistance compared to alloys like 6061. The magnesium content is also critical: at 1.2–1.8%, it promotes the formation of Al₂CuMg (S phase) precipitates, which provide additional strengthening during artificial aging. Manganese (0.3–0.9%) forms Al₆Mn dispersoids that pin grain boundaries, preventing recrystallization during heat treatment. The iron and silicon impurities are kept below 0.50% each to avoid forming brittle Al₇Cu₂Fe and Mg₂Si phases, which can reduce ductility and fatigue life. For critical aerospace applications, we at Dongguan Stirling Metal Products Co., Ltd. recommend specifying the tighter composition limits (e.g., Cu 4.2–4.7%, Mg 1.4–1.6%) to ensure consistent mechanical properties.
3. Mechanical & Physical Properties
2024 aluminum alloy exhibits a wide range of properties depending on temper. The T3 and T4 tempers are most common for aerospace applications due to their combination of high strength and good formability. Below are typical values for the T3 temper (sheet) and T6 temper (bar stock):
| Property | T3 Temper (Sheet) | T6 Temper (Bar) | Unit |
|---|---|---|---|
| Tensile Strength (Ultimate) | 470–510 | 480–520 | MPa |
| Yield Strength (0.2% offset) | 345–380 | 395–430 | MPa |
| Elongation (in 50 mm) | 12–18 | 8–12 | % |
| Hardness (Brinell HB 500 kg/10 mm) | 120–130 | 135–145 | HB |
| Hardness (Rockwell B) | 75–82 | 82–88 | HRB |
| Shear Strength | 285–310 | 300–325 | MPa |
| Fatigue Strength (10⁷ cycles, R=0.1) | 140–170 | 150–180 | MPa |
| Modulus of Elasticity | 73.1 | 73.1 | GPa |
| Poisson’s Ratio | 0.33 | 0.33 | — |
| Density | 2.78 | 2.78 | g/cm³ |
| Thermal Conductivity (at 25°C) | 121–151 | 121–151 | W/m·K |
| Electrical Conductivity | 30–40 | 30–40 | %IACS |
| Specific Heat Capacity | 875 | 875 | J/kg·K |
| Melting Range (solidus–liquidus) | 502–638 | 502–638 | °C |
| Thermal Expansion (20–100°C) | 23.2 | 23.2 | µm/m·°C |
These properties make 2024 ideal for structural components where weight savings are critical. For example, in aircraft wing skins, the high fatigue strength (140–170 MPa) ensures long service life under cyclic loading. The thermal conductivity (121–151 W/m·K) is moderate, which influences CNC machining heat dissipation—a key consideration for our engineers at Dongguan Stirling Metal Products Co., Ltd. The electrical conductivity of 30–40% IACS is relatively low compared to pure aluminum (62% IACS), which is due to the scattering of electrons by copper and magnesium atoms in solid solution. The specific heat capacity of 875 J/kg·K means that 2024 requires more energy to heat than some other alloys, which affects both heat treatment and machining thermal management. The melting range of 502–638°C is relatively narrow, requiring careful control during solution heat treatment (typically at 495–505°C) to avoid incipient melting of eutectic phases. For comparison, 2024-T3 has a fatigue strength that is approximately 30% higher than 6061-T6 (105 MPa), making it the preferred choice for primary aircraft structures.
4. CNC Machining Characteristics
2024 aluminum alloy is classified as having excellent machinability, with a machinability rating of 70–80% compared to free-machining brass (100%). However, its high strength and tendency to form built-up edge (BUE) require optimized parameters. Below are our recommended CNC machining parameters for 2024 in the T3/T4 temper:
| Parameter | Roughing | Finishing | Unit |
|---|---|---|---|
| Cutting Speed (vc) | 200–350 | 350–500 | m/min |
| Feed Rate (f) | 0.15–0.30 | 0.05–0.15 | mm/rev |
| Depth of Cut (ap) | 2.0–5.0 | 0.2–1.0 | mm |
| Spindle Speed (for 10 mm tool) | 6,000–11,000 | 11,000–16,000 | RPM |
| Tool Material | Carbide (K10/K20) | PCD or CVD Diamond | — |
| Tool Geometry (rake angle) | 10–15° positive | 15–20° positive | degrees |
| Coolant | Flood coolant (water-soluble oil, 5–8% concentration) | MQL or mist (0.5–1.0 ml/min) | — |
| Surface Finish (Ra) | 1.6–3.2 | 0.4–0.8 | µm |
| Expected Tool Life (carbide insert) | 30–60 | 60–120 | minutes |
Key machining considerations for 2024 include:
- Chip Control: 2024 produces long, stringy chips that can entangle. Use chip breakers or high-pressure coolant (50–70 bar) to break chips into manageable “figure-9” shapes. For roughing operations, we recommend a chip thickness of 0.02–0.05 mm per tooth to ensure efficient chip evacuation.
- Built-Up Edge (BUE): At cutting speeds below 150 m/min, BUE can form, degrading surface finish. Maintain speeds above 200 m/min for finishing. The BUE is caused by adhesion of aluminum to the tool edge due to the high affinity between aluminum and carbide; using PCD tools eliminates this issue entirely.
- Heat Generation: Despite moderate thermal conductivity, 2024 work-hardens rapidly. Avoid dwell marks or interrupted cuts that cause localized heating above 150°C, which can soften the T3 temper. The work-hardening rate of 2024 is approximately 0.3–0.5 MPa per 1% strain, which is higher than 6061 (0.2–0.3 MPa per 1% strain).
- Tool Wear: Abrasive wear from copper-rich particles is common. Use coated carbide (TiAlN or AlCrN) for roughing and PCD for finishing to achieve tolerances of ±0.01 mm. The copper content (3.8–4.9%) creates hard intermetallic particles (Al₂Cu) that act as abrasive agents, accelerating flank wear by 20–30% compared to 6061.
- Stress Relief: For large parts, consider stress-relieving (T351 temper) to minimize distortion during machining. At Dongguan Stirling Metal Products Co., Ltd., we often specify T351 for components over 300 mm in length. The stress relief process involves stretching the material by 1–3% after solution treatment, which reduces residual stresses from 150–200 MPa to below 50 MPa.
For comparison, 2024 machines better than 7075 (which is more abrasive) but requires sharper tools than 6061. Our CNC department typically uses 4-flute carbide end mills with a 45° helix angle for optimal chip evacuation. For high-speed machining (HSM) operations, we employ trochoidal milling paths that maintain a constant chip load, reducing cutting forces by 30–40% and extending tool life by 50%. The recommended cutting fluid for 2024 is a semi-synthetic coolant with a concentration of 7–10%, which provides excellent lubrication and corrosion inhibition. For deep-hole drilling (L/D > 5), we use peck drilling cycles with a peck depth of 0.5–1.0 mm to prevent chip clogging and tool breakage.
5. Applications
2024 aluminum alloy is the backbone of aerospace structures, but its use extends to many high-performance industries:
- Aerospace: Aircraft fuselage skins, wing panels, ribs, and stringers (e.g., Boeing 737 wing skins use 2024-T3). Also used in helicopter rotor hubs and missile fins. The alloy accounts for approximately 30% of the structural weight of modern commercial aircraft, with over 50,000 tons used annually in aerospace manufacturing.
- Automotive: Lightweight chassis components, suspension arms, and brake calipers in racing cars (Formula 1 uses 2024 for certain structural brackets). The high fatigue strength (140–170 MPa) makes it ideal for suspension components that experience cyclic loading of 10–20 kN during a race.
- Defense: Armor plating for military vehicles (due to high ballistic resistance), firearm receivers, and missile casings. 2024-T3 has a ballistic limit of 850–900 m/s for 7.62 mm AP projectiles at a thickness of 25 mm, making it suitable for lightweight armor applications.
- Electronics: Heat sinks for high-power LEDs and RF amplifiers, where thermal conductivity (121–151 W/m·K) is adequate. The alloy’s electrical conductivity (30–40% IACS) is sufficient for grounding and shielding applications in electronic enclosures.
- Sports Equipment: Bicycle frames (high-end racing bikes), golf club shafts, and baseball bats. The specific strength (tensile strength/density) of 2024-T6 is 173–187 kN·m/kg, which is 20–30% higher than 6061-T6 (140–150 kN·m/kg).
- CNC Machined Parts: Precision components like jigs, fixtures, and prototype parts requiring high strength and tight tolerances (±0.01 mm). At Dongguan Stirling Metal Products Co., Ltd., we have supplied 2024 CNC machined parts for UAV frames, satellite components, and medical imaging equipment where weight and strength are critical.
In the aerospace sector, 2024 is often used in combination with 7075 for different structural roles: 2024 for tension-dominated components (wing skins, fuselage panels) and 7075 for compression-dominated components (spars, ribs). The alloy’s excellent fatigue crack growth resistance (da/dN = 1.5–2.5 × 10⁻⁶ mm/cycle at ΔK = 10 MPa√m) ensures safe-life design for critical aircraft structures. For military applications, 2024-T3 is specified in MIL-DTL-6088 for armor plate, with a minimum tensile strength of 470 MPa and a minimum elongation of 12%.
6. Why Choose Dongguan Stirling Metal Products Co., Ltd.
Dongguan Stirling Metal Products Co., Ltd. is your trusted partner for 2024 aluminum alloy CNC machining. With over 15 years of experience in precision manufacturing, we offer:
- Material Expertise: We source 2024 from certified mills (Alcoa, Kaiser, Constellium) with full MTC (Mill Test Certificate) traceability. We stock T3, T4, T6, and T351 tempers in sheet, plate, bar, and custom extrusions. Our inventory includes thicknesses from 0.5 mm to 200 mm and widths up to 1500 mm.
- Advanced CNC Capabilities: Our 5-axis DMG MORI and Mazak machining centers achieve tolerances of ±0.005 mm on critical features. Surface finishes down to Ra 0.2 µm are possible with diamond tooling. We have 30 CNC machines with spindle speeds up to 20,000 RPM and feed rates up to 30 m/min.
- Process Optimization: We use CAM software (Mastercam 2024) with dynamic milling strategies to reduce cycle times by 20–30% while maintaining tool life. Our proprietary coolant system maintains chip temperature below 80°C to preserve material properties. We also employ adaptive machining techniques that adjust feed rates in real-time based on cutting force feedback.
- Quality Assurance: Every part undergoes CMM inspection (Zeiss Contura G2) with ISO 2768-m tolerance verification. We provide full dimensional reports and material certifications. Our quality management system is ISO 9001:2015 and AS9100D certified for aerospace applications.
- Surface Treatment: In-house anodizing (Type II and III) to MIL-A-8625F, plus chromate conversion, sandblasting, and powder coating. For 2024, we recommend sulfuric acid anodizing (20–25 µm thickness) for corrosion protection. We also offer hard anodizing (Type III) with thicknesses up to 75 µm for wear-resistant applications.
- Lead Times: Prototypes in 3–5 business days, production orders in 7–15 days. We offer 24/7 rush service for critical aerospace projects. Our average on-time delivery rate is 98.5% over the past 12 months.
- Cost Efficiency: Our pricing for 2024 CNC parts starts at $15–25 per piece for simple geometries, with volume discounts for orders over 1,000 units. Material costs: sheet $8–12/kg, bar $10–15/kg (FOB Shenzhen). We also offer consignment inventory programs for high-volume production runs.
Contact us today for a free quote on your 2024 aluminum alloy project. Our engineering team will review your drawings and recommend the optimal temper, machining strategy, and surface finish to meet your performance requirements. We provide free DFM (Design for Manufacturing) analysis and can suggest design modifications to reduce machining costs by up to 25%. With our combined expertise in material science and CNC machining, Dongguan Stirling Metal Products Co., Ltd. is your one-stop solution for high-quality 2024 aluminum components.
