2024 Aluminum Alloy: Properties, Tempers & Uses
2024 is a heat-treatable aluminum alloy strengthened mainly with copper and magnesium. It is widely used in aircraft structures and machined parts that need high strength at low weight. Its main trade-offs are corrosion protection and difficult fusion welding. To choose it correctly, specify the temper, product form and thickness—not just “2024 aluminum.”
What is 2024 aluminum used for?
2024 belongs to the 2xxx series of wrought aluminum alloys. “Wrought” means the material is worked into products such as rolled sheet, plate or bar, rather than used as a casting alloy. Its best-known uses include aircraft skins, ribs, tension members and structural fittings. It also suits selected machined parts where weight and load capacity matter.
The useful question is not simply whether 2024 is strong. It is whether that strength fits the way the part will be made, joined and exposed in service.
- Riveted sheet structures
- 2024 sheet can be a useful choice when the design includes suitable fatigue data, fastener details and corrosion protection.
- Machined fittings or plates
- A specified stress-relieved temper can help manage movement during machining. It does not remove the need to control workholding and material removal.
- Welded frames
- Do not make 2024 the default. A more weldable alloy, often 6061 where its properties suit the design, usually offers a simpler starting point.
- Wet or salt-exposed parts
- Allow for protective finishes, joint sealing and inspection. Bare 2024 is not a maintenance-free substitute for a corrosion-resistant alloy.
Application context: Alcoa 2024 sheet and plate data. The machining and selection points are engineering considerations, not approval of a particular part.
What is 2024 aluminum made of?
Copper and magnesium are the main strengthening additions. Manganese also helps control the alloy’s structure. The rest is mainly aluminum, with limits on other elements.
Swipe horizontally to read the complete table.
| Element | Specified range or maximum | How to read it |
|---|---|---|
| Copper, Cu | 3.8–4.9% | Main alloying addition |
| Magnesium, Mg | 1.2–1.8% | Works with copper in age hardening |
| Manganese, Mn | 0.30–0.90% | Controlled alloying addition |
| Silicon / iron | 0.50% maximum each | Separate limits, not 0.50% combined |
| Chromium / zinc / titanium | 0.10% / 0.25% / 0.15% maximum | Maximum values in the same order |
| Other elements / aluminum | Others: 0.05% each, 0.15% total; aluminum: balance | Use the applicable purchase specification and mill certificate for acceptance. |
Source: Kaiser Aluminum 2024 technical data, page 2.
Why heat treatment changes its strength
Heat treatment allows very small particles, called precipitates, to form inside the metal. These particles make it harder for the structure to slip permanently under load. Cold working can add further strengthening.
That is why two pieces with the same 2024 chemistry can behave differently. One may be soft enough for forming; another may resist much higher loads but tolerate less bending before cracking. The temper suffix tells you which processing condition you are buying.
What is the difference between 2024-T3 and T351?
T3 identifies a solution-heat-treated, cold-worked and naturally aged condition. T351 adds a specified stretching treatment for stress relief. T3 is commonly encountered in sheet; T351 is common in plate. Neither suffix, by itself, gives every strength or dimensional requirement.
Solution heat treatment and quenching prepare the alloy for strengthening. Natural aging happens at room temperature; artificial aging uses a controlled elevated temperature. Stretching reduces residual stress—the internal stress left after processing.
Swipe horizontally to compare temper definitions and practical limits.
| Condition | Processing meaning | Practical consequence |
|---|---|---|
| O | Annealed | Soft condition for easier forming; not a substitute for a high-strength finished temper. |
| T3 | Solution heat treated, cold worked, then naturally aged | Common sheet condition. Use bend data for the actual thickness and grain direction. |
| T4 | Solution heat treated and naturally aged | No deliberate strengthening cold-work step as in T3. Do not substitute T4 for T3 without approval. |
| T351 | Solution heat treated, stress relieved by stretching, then naturally aged | Useful for machining from plate; reduced residual stress does not mean zero distortion. |
| T81 / T851 | T8-family processing includes cold work before artificial aging; T851 includes stretching for stress relief | Different strength and ductility balance. Use the specific product data, not an assumed “upgrade” from T3 or T351. |
Temper basis: U.S. Air Force technical manual TO 1-1A-9, aluminum temper designations. Product availability and permitted substitutions still depend on the governing specification.
Alclad is not a temper. “Alclad 2024-T3” describes both the surface construction and the temper of the core alloy. “2024-T3” alone does not tell you whether the product is clad.
You may also encounter T6 or more specific temper suffixes. Do not order by the familiar-looking number alone: confirm that the exact alloy, temper and product form are covered by the drawing and the supplier’s certification.
How strong is 2024 aluminum?
Strength depends on temper, product form, thickness, test direction and whether the material is bare or clad. Yield strength describes the onset of a specified amount of permanent deformation. Ultimate tensile strength is the highest tensile stress reached during the test; it is not a safe working stress.
The table below shows why “2024 strength” needs a qualification. It summarizes an Alcoa sheet-and-plate data sheet; the ranges cover different thickness entries, not the spread of results from one batch.
Swipe horizontally to see thickness ranges and both strength values.
| Product / temper | Thickness range | Ultimate tensile strength | Yield strength |
|---|---|---|---|
| T3 flat sheet | 0.008–0.249 in. 0.203–6.32 mm | 434–441 MPa 63–64 ksi | 289 MPa 42 ksi |
| T351 plate | 0.250–4.000 in. 6.35–101.60 mm | 393–441 MPa 57–64 ksi | 282–289 MPa 41–42 ksi |
| T81 flat sheet | 0.010–0.249 in. 0.254–6.32 mm | 462 MPa 67 ksi | 400 MPa 58 ksi |
Source: Alcoa Alloy 2024 Sheet and Plate, bare-product table, hosted by Howard Precision Metals. This is a historical product reference, not a current procurement specification or a design-allowables table. The source notes decreasing T351 strength with increasing thickness.
Why a “typical” value can be higher
Kaiser lists typical T4/T351 tensile and yield values of 469 MPa and 324 MPa for its stated specimen basis. That does not conflict with lower product minimums: a typical result and a required minimum answer different questions.
For purchasing, compare the mill certificate with the exact specification, temper, thickness and test direction. For structural design, use the approved allowable and relevant failure checks. Do not use a generic datasheet value as either one.
Typical-data basis: Kaiser 2024, page 1; the table identifies a 0.500-in.-diameter tensile specimen. These values are not presented here as a T3 sheet guarantee.
Example: reading a plate quote correctly
A quote saying only “2024, 469 MPa tensile” leaves key questions unanswered. Is it T351 plate or another product? Is 469 MPa a typical value or a guaranteed minimum? Which thickness and test direction apply? A useful quote identifies those conditions and supplies traceable certification.
What are its density, stiffness and thermal properties?
These properties help with weight, deflection and temperature calculations. They do not replace the strength and fatigue checks for the actual part.
Swipe horizontally to read the value and its temperature or temper basis.
| Property | Value | Basis or limitation |
|---|---|---|
| Density | 2.77 g/cm³ 2,770 kg/m³ | Nominal, at 20°C |
| Young’s modulus | 73.1 GPa About 10.6 million psi | Typical elastic modulus; not yield strength |
| Thermal expansion | 22.9 µm/(m·K) | Average linear coefficient over 20–100°C |
| Thermal conductivity | 120 W/(m·K) | T4/T351 at 20°C; other tempers differ |
| Melting range | 502–638°C 936–1,180°F | An alloy melts over a range; this is not its allowable service temperature. |
Source: Kaiser 2024 technical data. Values are rounded reference data.
Higher strength does not automatically mean less bending
Young’s modulus describes stiffness while deformation is still elastic. Changing the temper can change yield strength greatly, while leaving stiffness much less changed. A thin 2024 part can therefore deflect too much without coming close to its yield strength. Section thickness, shape and support spacing may matter more than a stronger temper.
Temperature also matters before melting begins. Heating can alter the temper and reduce useful properties. A melting-point number cannot tell you whether a part will remain strong during a paint bake, joining process or sustained hot service.
Why is 2024 used in parts under repeated loading?
Fatigue is damage caused by repeated loading, even when each load is below the material’s static strength. A small crack can start at a hole, scratch, sharp corner or corroded area and then grow over many cycles. This is why aircraft material selection considers more than tensile strength.
2024 has a long history in fatigue-sensitive structures. That history is useful, but it does not provide one safe fatigue stress for every component. Surface condition, mean load, stress range, part geometry, grain direction, environment and inspection strategy all affect the result.
Published test example: a notch changes the question
Alcoa’s fatigue chart states a notch factor of Kt = 3 and a load ratio of R = 0. These describe the specimen’s stress concentration and loading cycle. Its curve is not a universal limit for a smooth bar, a fastener joint or a corroded sheet.
The practical lesson: select fatigue data for the actual loading and geometry, then consider how a crack would be found before it became critical.
Test context: Alcoa 2024, axial-stress notch fatigue chart. No fatigue-life prediction for a customer part is made here.
For a fatigue-critical design, stop if the available data do not match the product, orientation or loading condition. A higher tensile value alone is not enough to justify a thinner section or a longer inspection interval.
Does 2024 aluminum corrode, and what does Alclad do?
Yes. Aluminum does not form red iron rust, but 2024 can still corrode. Copper-rich high-strength alloys need particular attention in wet, salty or industrial environments. Protection is especially important where moisture can remain between joined surfaces.
Alclad adds a protective outer layer
Alclad 2024 has a metallurgically bonded, more corrosion-resistant aluminum layer over the core. The layer provides surface protection and can corrode preferentially to help protect the stronger core beneath it.
It is not the same as paint, and it does not make every cut edge or drilled hole immune to attack. Bare and clad products can also have different specified mechanical properties.
Protect the joints as well as the visible faces
Choose the approved finish for the exposure and service requirements. Pay attention to cut edges, fastener holes, trapped moisture and contact with dissimilar metals. Conversion coatings, anodizing, primers or sealants may be part of a specified protection system; they are not interchangeable treatments.
During cleaning or repair, preserve the intended surface construction. Aggressive abrasion or uncontrolled material removal can thin the cladding or change dimensions. A shiny surface is not proof that the original protection remains intact.
Protection principles: TO 1-1A-9, aluminum-alloy handling and clad material. Follow the applicable component maintenance instructions for a real repair.
Can you machine, bend or weld 2024 aluminum?
These are three different manufacturing questions. 2024 is useful for many machined parts, forming depends strongly on temper, and conventional fusion welding is a major limitation.
Machining: manage movement, not just cutting speed
For a pocketed part cut from plate, T351 is often considered because stretching reduces residual stress. Heavy or uneven stock removal can still release stress and move the part. Excessive clamping force can also hide distortion until the fixture is released.
Plan roughing and finishing stages, leave suitable finishing stock, and inspect after unclamping. A flat blank and an accurate toolpath do not guarantee a flat finished part.
Forming: check temper, thickness and grain direction
Annealed O material is easier to bend than a high-strength temper. But if the finished design requires T3 or another strengthened condition, forming in O introduces a controlled heat-treatment route that must be planned and qualified.
Do not copy a bend radius from a different thickness or alloy. Use the applicable bend table and grain orientation, deburr edges and test the intended bend. Stop if cracking appears; forcing the bend further is not a way to recover the material.
Welding: hot cracking and local softening are the main concerns
2024 is not a routine choice for fusion-welded structures. Its copper–magnesium chemistry makes cracking during solidification a concern. Welding heat can also change the strengthened condition in the heat-affected zone, which is the base metal heated beside the weld.
A narrow laser weld does not automatically remove these metallurgical risks. A neat surface bead is not enough to prove crack resistance, joint strength or fatigue life. Any proposed process needs specialist development and qualification for the actual alloy, temper, joint and service.
For new designs, consider whether mechanical fastening or a more weldable alloy better suits the job. If a qualified drawing specifies 2024, do not change either the material or joining method without design approval.
Welding basis: ESAB’s aluminum welding guidance. For the broader process issues, see why aluminum welding is difficult.
2024 vs 6061 vs 7075: which alloy should you choose?
Choose for the part and manufacturing route, not the highest strength number. The temper matters in every comparison. For example, 7075-T6 and an overaged 7075 temper do not offer the same strength–corrosion balance.
Swipe horizontally to compare the three material choices.
| Alloy | A useful starting point when… | Check before choosing |
|---|---|---|
| 2024 | You need high-strength sheet or machined components, with suitable fatigue and damage-tolerance data. | Corrosion protection, joining method, temper, grain direction and product thickness. |
| 6061 | Welded fabrication, corrosion resistance and general-purpose manufacture drive the design. | Whether its strength is sufficient, including the reduced strength around a weld. |
| 7075 | High static strength is a leading requirement for a mechanically joined or machined part. | Exact temper, corrosion and fracture requirements, manufacturing route and poor routine fusion weldability. |
Comparison basis: Kaiser 6061 data and Kaiser 7075 rod and bar data. Product-specific figures must not be transferred between sheet, plate and bar.
Design example: one bracket, two manufacturing routes
A bracket welded from several pieces may favor 6061 if the welded design meets the load requirement. A bracket machined from one piece may justify evaluating 2024 or 7075. The comparison must include weight, stiffness, fatigue, protection and manufacturing cost—not just the blank’s tensile strength.
This is a selection example, not a claim that one alloy can directly replace another in an approved design.
For more detail, read the 6061 aluminum guide or the 7075 aluminum guide.
What should a 2024 aluminum material order specify?
A clear purchase description prevents mistakes that a chemistry check alone will not catch. Start with the drawing, then make sure the quotation and certificate describe the same material.
- Alloy, exact temper and product formFor example, distinguish T3 sheet from T351 plate. Do not assume a supplier’s stock temper is an approved substitute.
- Bare or clad constructionState whether Alclad is required and which product specification defines the cladding. Include any surface or finish requirements.
- Dimensions and orientationInclude thickness, size, tolerances, flatness and any required grain direction or machining allowance.
- Governing specification and revisionUse the standard required by the design. ASTM B209/B209M covers relevant sheet and plate products; bar or aerospace-specific requirements may need a different specification.
- Certification and traceabilityRequest the required chemistry and mechanical test results, material identification and lot traceability. Check that the test direction and applicable property limits match the product.
Do not accept an unexplained change in temper, thickness class or clad condition. Resolve the mismatch before machining or releasing the material to production.
Specification scope: ASTM B209/B209M. The linked edition explains the scope; the contract must identify the edition actually required.
Planning a cleaning or joining step on 2024?
Share the exact temper, bare or clad condition, thickness, surface treatment and required result with Oceanplayer Laser. These details help define what a sample evaluation must check. A sample trial does not replace the design approval or qualification required for a critical component.
Discuss your material and processTechnical references
The following references support the property values, temper explanations and manufacturing limits. Published product data are not a replacement for current contractual specifications or approved design allowables.
- Kaiser Aluminum: 2024 sheet, coil and plate — composition and typical properties.
- Alcoa: Alloy 2024 Sheet and Plate — historical product minimums and fatigue test conditions.
- U.S. Air Force: TO 1-1A-9 — aluminum tempers, forming and material handling.
- ESAB: Selecting the Right Filler Alloy for Aluminum Welding — hot cracking and heat-affected-zone properties.
- Kaiser Aluminum: 6061 and 7075 rod and bar — comparison context.
- ASTM B209/B209M — sheet and plate specification scope.