Aluminum 2024 properties
Aluminum 2024 (EN AW‑AlCu4Mg1) is a heat-treatable 2000 series alloy whose main alloying element is copper. With a density of only 2.78 g/cm³ and a tensile strength that can exceed 450 MPa in T8 temper, it offers an exceptional strength-to-weight ratio for structural components subjected to cyclic loads. Its use is widespread in the aerospace industry and in applications where fatigue is a critical criterion.
Chemical Composition
Section titled “Chemical Composition”The chemical composition of aluminum 2024, according to EN 573‑3, has very tightly controlled limits of alloying elements that define its precipitation‑hardening capability. Aluminum acts as the base metal and the remaining components are adjusted to the following ranges:
| Element | Minimum (mass %) | Maximum (mass %) |
|---|---|---|
| Aluminum (Al) | 90.7% | Balance |
| Copper (Cu) | 3.8% | 4.9% |
| Magnesium (Mg) | 1.2% | 1.8% |
| Manganese (Mn) | 0.3% | 0.9% |
| Silicon (Si) | — | 0.5% |
| Iron (Fe) | — | 0.5% |
| Zinc (Zn) | — | 0.25% |
| Titanium (Ti) | — | 0.15% |
| Chromium (Cr) | — | 0.1% |
| Other elements (each) | — | 0.05% |
| Other elements (total) | — | 0.15% |
Zr combined with Ti may be raised up to 0.20% in extruded or forged products. This strict compositional window, especially for Cu and Mg, enables the formation of the intermediate precipitates responsible for hardening.
Physical Properties
Section titled “Physical Properties”The density of aluminum 2024 is 2.78 g/cm³ (0.1 lb/in³), approximately 65% lower than that of most steels, making it a preferred material for lightweight structures. The fundamental properties are summarized below:
| Property | SI Value | Imperial Value |
|---|---|---|
| Density (ρ) | 2.78 g/cm³ = 2780 kg/m³ | 0.1 lb/in³ |
| Modulus of Elasticity (E) | 73.1 GPa | 10.6 × 10⁶ psi |
| Shear Modulus (G) | 27.6 GPa | 4.0 × 10⁶ psi |
| Melting start temperature (solidus) | 500 °C | 932 °F |
Thermal Properties
Section titled “Thermal Properties”The thermal conductivity of aluminum 2024 is 121 W/(m·K), a moderate value within the aluminum alloy family, allowing heat dissipation in mechanical components. The main thermal magnitudes are detailed:
| Property | SI Value | Imperial Value |
|---|---|---|
| Thermal conductivity (λ) | 121 W/(m·K) | 840 BTU·in/(hr·ft²·°F) |
| Specific heat (cₚ) | 875 J/(kg·K) | 0.209 BTU/(lb·°F) |
| Coefficient of thermal expansion (α) (20‑100 °C) | 22.9 µm/(m·K) | 12.7 × 10⁻⁶ in/(in·°F) |
| Maximum service temperature (Tmax) | 120 °C | 248 °F |
Mechanical Properties by Temper
Section titled “Mechanical Properties by Temper”The mechanical characteristics of 2024 vary radically depending on the heat treatment and the degree of cold work applied. In the annealed condition (O) it barely reaches 220 MPa tensile strength, while in T8 temper it exceeds 450 MPa. The following table shows typical values for the most common tempers:
| Temper | Tensile strength (Rm) | Yield strength (Rp0.2) | Elongation (A) | Brinell hardness (HBW) |
|---|---|---|---|---|
| O (annealed) | 220 MPa (32 ksi) | 140 MPa (20 ksi) | 12‑13% (Lo=50 mm) | 55 |
| T3 (solution treated, cold worked, naturally aged) | 395‑450 MPa (57‑65 ksi) | 270‑310 MPa (39‑45 ksi) | 6‑8% (Lo=50 mm) | 120 |
| T4 (solution treated, naturally aged) | 427 MPa (62 ksi) | 276 MPa (40 ksi) | 10‑15% | — |
| T351 (solution treated, stress relieved) | 470 MPa (68 ksi) | 280 MPa (41 ksi) | 20% | — |
| T8 (solution treated, cold worked, artificially aged) | 455 MPa (66 ksi) | 380 MPa (55 ksi) | 4‑5% (Lo=50 mm) | 130 |
The strength values in T3 and T4 come from industrially accepted averages; the minimum elongation in T351 highlights the ductility improvement provided by stress relief.
Electrical Properties
Section titled “Electrical Properties”The electrical conductivity of aluminum 2024 is 30% IACS (International Annealed Copper Standard). This figure corresponds to about 17.4 MS/m and reflects the influence of alloying elements in solution, which drastically reduce electron mobility compared to pure aluminum (≈ 62% IACS). The alloy is used in structures where conductivity is not a priority requirement; when electrical performance is needed, 6061 or 1xxx series are usually preferred.
Corrosion Resistance
Section titled “Corrosion Resistance”Aluminum 2024 exhibits notably low corrosion resistance due to the high copper concentration, which promotes the formation of galvanic couples in the presence of moisture. For this reason, in atmospheric or marine environments it is frequently used as alclad sheet (coated with a thin layer of pure aluminum or Al‑1Zn), which sacrifices the external surface to protect the core. However, the alclad process can slightly reduce fatigue strength. Uncoated machined parts require protection systems such as anodizing, painting, or inhibitor coatings.
Weldability
Section titled “Weldability”Aluminum 2024 is not weldable by fusion welding techniques (TIG, MIG, laser), as its chemical composition causes solidification defects—hot cracking—during re-solidification of the weld pool. The only joining technology authorized in production for this alloy is friction stir welding (FSW), which operates in the solid state without reaching material fusion and maintains microstructural integrity. Any attempt at arc welding requires a careful risk assessment and is usually contraindicated in critical structural applications.
Machinability
Section titled “Machinability”The machinability of aluminum 2024 is considered medium, below specific alloys such as 2011 or 6262, but notably better than that of 7075 in T6 temper. In T3 or T4 temper it produces fragmented chips and offers acceptable surface finish with carbide tools and adequate lubrication. Milling, turning, and drilling operations are common in the manufacture of mechanical components; selection of cutting edges and moderate speeds helps avoid premature dulling.
Applications by Industry
Section titled “Applications by Industry”The combination of high specific strength and good fatigue toughness makes 2024 an irreplaceable structural material in multiple sectors:
- Aerospace: Wing and fuselage skins, bulkheads, stringers, and fittings subjected to tension and cyclic loads.
- High-performance automotive: Connecting rods, pistons, bearing housings, and transmission components where every gram counts.
- Machinery: Gears, camshafts, supports, and machined parts with strength and low inertia requirements.
- Military industry: Structural components of unmanned aerial vehicles (UAVs) and light weapon systems.
- Mold and tooling: Precision mold parts for short series requiring good thermal conductivity.
Comparison with Similar Materials
Section titled “Comparison with Similar Materials”Compared to other structural aluminum alloys, 2024 occupies an intermediate position in strength, but stands out for its fatigue behavior and ease of machining in natural temper. The following table illustrates its main differences with 2014, 6061, and 7075:
| Property | 2024‑T3/T4 | 2014‑T6 | 6061‑T6 | 7075‑T6 |
|---|---|---|---|---|
| Tensile strength (Rm, MPa) | 427‑441 (T4/T3) | 455‑460 | 310 | 540‑572 |
| Yield strength (Rp0.2, MPa) | 276‑290 | 400 | 276 | 503 |
| Typical elongation (%) | 10‑15 | 10 | 12 | 11 |
| Brinell hardness (HBW) | 120 | 130 | 95 | 150 |
| Weldability (fusion) | No | No (similar) | Excellent | Poor |
| Corrosion resistance | Low | Low | High | Low |
| Machining | Medium | Medium-high | Medium | Medium-low |
2014 and 2024 share the same alloy philosophy (Al‑Cu), but 2014 is preferred for forging while 2024 is used in sheet and plate. 6061 offers lower strength but gains in weldability and corrosion protection. 7075, on the other hand, reaches the highest strengths in the aluminum family, albeit with lower ductility and greater sensitivity to stress concentration.
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the tensile strength of aluminum 2024 in T3 temper?
Section titled “What is the tensile strength of aluminum 2024 in T3 temper?”The tensile strength of 2024‑T3 is in a typical range of 395 to 450 MPa (57‑65 ksi), with an average value of 441 MPa (64 ksi).
What is the yield strength of aluminum 2024‑T4?
Section titled “What is the yield strength of aluminum 2024‑T4?”The yield strength of 2024‑T4 is 276 MPa (40 ksi) as an industrial characteristic value, reaching a minimum permanent set of 0.2%.
What hardness is aluminum 2024 supplied in?
Section titled “What hardness is aluminum 2024 supplied in?”The Brinell hardness of 2024 depends on the temper: 55 HBW in O condition, 120 HBW in T3, and up to 130 HBW in T8, providing a direct reference to its mechanical strength.
Up to what temperature can aluminum 2024 work?
Section titled “Up to what temperature can aluminum 2024 work?”Aluminum 2024 maintains its mechanical properties up to a maximum service temperature of 120 °C (248 °F); above this value the strength drops rapidly and the material begins overaging processes.
Can aluminum 2024 be welded?
Section titled “Can aluminum 2024 be welded?”No; aluminum 2024 is not suitable for fusion welding. It is only weldable by friction processes (FSW), which avoid the formation of solidification cracks characteristic of this alloy.
What differentiates aluminum 2024 from 7075?
Section titled “What differentiates aluminum 2024 from 7075?”2024 offers lower tensile strength (about 440 MPa in T3 versus 572 MPa for 7075‑T6), but leads to better fracture toughness and lower notch sensitivity, making it more suitable for components subjected to fatigue.
References
Section titled “References”- azom.com: https://www.azom.com/article.aspx?ArticleID=23683
- engineeringtoolbox.com: https://www.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.html
- steelnumber.com: https://www.steelnumber.com/en/steel_alloy_composition_eu.php?name_id=1036