What Is 2024 Aluminum?
2024 is a 2000-series alloy with copper as its primary alloying element (3.8–4.9% Cu). It gains strength through precipitation hardening after solution heat treatment, not from cold working, which places it among the strongest wrought aluminum alloys.
That copper content also makes 2024 the least corrosion-resistant of the common aerospace alloys and generally unsuitable for fusion welding — bare sections are prone to intergranular and exfoliation corrosion and require cladding, anodizing, or paint for protection. It is this strength-to-weight profile, paired with reliable machinability, that makes 2024 the default choice for airframes and high-performance structural parts — and exactly why the specified temper and product form, especially for extruded sections, matters more than the alloy name alone.
Understanding the T3511 Temper
The “T3511” designation describes a three-stage thermal-mechanical treatment applied to extruded 2024 products:
- Solution heat treatment. The extrusion is heated to roughly 493°C (920°F) to dissolve copper-rich precipitates into a uniform solid solution, then rapidly quenched — typically in cold water.
- Stress relief by stretching. Within a short window after quenching, the material is stretched 1–3% of its length. This controlled plastic deformation relaxes the residual stresses locked in by the rapid quench.
- Straightening. Because T3511 is assigned to extrusions (rod, bar, shape, tube, profile), the section is additionally straightened by light cold work so it meets straightness tolerances as delivered.
The practical result is an extruded 2024 section that combines high strength with low residual stress and good as-received straightness. The benefit appears during machining: a T3511 bar or profile is far less likely to distort or spring out of tolerance than an unstressed extruded section when material is removed from one side.
How T3511 Differs from T351
T351 and T3511 share the same solution heat treatment and stretch stress relief. The extra “1” in T3511 is product-specific: it applies only to extrusions and adds a straightening step. T351 is the equivalent temper for plate and sheet, where stretching alone controls residual stress and straightness is governed by rolling. The distinction is product-form driven — T351 applies to flat rolled plate and sheet, T3511 to extruded bar, tube, shape, or profile.
2024-T3511 Mechanical Properties
The yield strength of 310 MPa is the number that drives most structural calculations. It leaves 2024-T3511 well above general-purpose 6061 (about 276 MPa) on strength, while the fatigue value around 125 MPa supports cyclic-load parts such as spars and fittings. The trade-off is corrosion and weldability, covered below.
| Eigendom | Waarde | Opmerking |
| Dichtheid | 2,78 g/cm³ | Typical for 2xxx-series |
| Uiteindelijke treksterkte | 425 MPa (62 ksi) | Extruded product, room temperature |
| Tensile Yield Strength (0.2% offset) | 310 MPa (45 ksi) | Key for structural design |
| Rek bij breuk | ~10% | Product-form dependent |
| Fatigue Strength (5×10⁸ cycles) | ~125 MPa (18 ksi) | Smooth specimen, R = −1 |
| Afschuifsterkte | 270 MPa (39 ksi) | Relevant for fastener joints |
| Elasticiteitsmodulus | 73 GPa (10.6×10³ ksi) | ~One-third of steel |
| Thermische geleidbaarheid | 121 W/m·K | Good heat dissipation |
| Thermische uitzettingscoëfficiënt | 23 µm/m·K | - |
| Specifieke warmtecapaciteit | 880 J/kg-K | - |
Where 2024-T3511 Is Used
The mix of strength, fatigue resistance, and post-machining dimensional stability makes T3511 the temper of choice for extruded sections in cyclic-load or precision structures.
Aerospace and Defense Structures
Wing spars, fuselage stringers, and structural fittings are often machined from 2024-T3511 extrusions because the stress-relieved condition keeps thin or asymmetric sections stable through milling. Missile fins, ordnance housings, and airborne electronics structures use the same temper where strength-to-weight and predictable machining behavior are primary requirements. In these applications the section is normally alclad or finish-protected, since bare 2024 does not survive aggressive environments unprotected.
High-Performance Machinery and Tooling
Motorsport suspension links, bell cranks, and gearbox casings machined from T3511 bar gain weight savings over steel without giving up stiffness. Precision jigs, inspection fixtures, and structural frames for automation use T3511 profile because it stays flat through temperature swings and repeated load cycles. Where the part is welded rather than fastened, 6061 is usually the better starting point — see the working notes below.
T3511 vs Other 2024 Tempers — How to Choose
When to Specify T3511
Two conditions point to T3511: the part is an extruded bar, tube, shape, or profile, and it will be precision-machined or carry cyclic load where distortion cannot be tolerated. If both hold, the stretch-and-straighten treatment reduces distortion and scrap risk during precision machining of extruded sections.
When Another Temper Fits Better
When the geometry is flat rolled, T351 plate or sheet gives the same stress relief without paying for extrusion tooling. When peak strength matters more than machinability or ductility, T851 delivers roughly 20% higher yield. When welding or saltwater service is part of the requirement, move off 2024 entirely — 6061 or a 5xxx alloy removes the corrosion and weldability limits at the cost of lower strength.
| Temper | Treatment | UTS | YS | Geschikt voor | Avoid when |
| T3511 | Solution + stretch + straighten (extrusion) | 425 MPa (62 ksi) | 310 MPa (45 ksi) | Machined extruded structures, dimensional stability | Welding required, saltwater exposure |
| T3 | Solution + cold work + natural age | 483 MPa (70 ksi) | 345 MPa (50 ksi) | Sheet skins, formed parts | Thick sections needing stability |
| T4 | Solution + natural age | 469 MPa (68 ksi) | 324 MPa (47 ksi) | High-ductility parts | Corrosion-exposed without cladding |
| T851 | Solution + stress relieve (stretch) + artificial aging | 510 MPa (75 ksi) | 450 MPa (66 ksi) | Maximum-strength parts | Ductility or formability needed |
Working with 2024-T3511 — What You Need to Know
Machining. 2024-T3511 machines cleanly with good chip control and supports high cutting speeds, which is why it is a staple for screw-machine products and precision CNC parts. Tool wear stays manageable because the alloy is not gummier than 6000-series material, but sharp tool geometry and consistent coolant flow keep surface finish tight on thin sections.
Welding and joining. Fusion welding is not recommended for 2024. The copper-rich composition makes the weld and heat-affected zone prone to hot cracking, and post-weld strength can fall well below the base material. For assemblies, use rivets, bolts, or adhesive bonding; if a welded structure is unavoidable, switch the design to 6061-T6 and accept the lower strength.
Corrosion protection. Bare 2024 has poor corrosion resistance and is vulnerable to intergranular and exfoliation attack, especially in chloride environments. Specify alclad (a metallurgically bonded pure-aluminum surface layer) for aircraft skins, or pair anodizing and paint for enclosed structures. In direct saltwater or marine immersion, 2024 is the wrong choice regardless of temper.
Formability. T3511 is delivered as a straightened extrusion, so it is not intended for heavy cold forming after treatment — bending risks cracking because the temper is already near peak strength. Form or shape the section before final aging where possible, or specify the geometry as an extrusion profile rather than bending from stock.
Pros and Limitations at a Glance
| Afmeting | Voordeel | Beperking |
| Strength-to-weight | Among the highest of wrought aluminum | - |
| Weerstand tegen vermoeiing | Strong for cyclic-load structures | Lower than 7075 at peak applications |
| Machining stability | Stress-relieved and straightened, low distortion | - |
| Corrosiebestendigheid | - | Poor; requires cladding or coating |
| Lasbaarheid | - | Fusion welding not recommended |
| Beschikbaarheid | Stock and custom extrusions available | Not a general sheet substitute |
| Kosten | - | Higher than 6061 |
Conclusie
2024-T3511 brings high strength, good fatigue resistance, and low machining distortion to extruded structural sections, but trades corrosion resistance and weldability for that performance — manageable only with the right protection and joining plan. Sourcing the correct extruded section with full documentation remains a common procurement challenge; Linsy Aluminum supplies 2024 alloy bar, tube, profile, and wire — including T3511 extrusions — with in-stock standard sizes, low-MOQ custom production (10–60 days), MTC for every order, SGS reports on request, and ISO 9001/14001/45001 certifications. Review the 2024-T3511 specification for mechanical property limits, temper comparison data, and available extrusion profiles, or contact Linsy Aluminum to confirm stock availability and custom production options for your project.
Veelgestelde vragen
Can 2024-T3511 be welded?
Fusion welding is not recommended. The copper-rich alloy cracks in the weld and heat-affected zone and loses much of its strength. Use mechanical fastening or adhesive bonding, or choose 6061-T6 if welding is required.
Is 2024-T3511 suitable for marine or saltwater use?
No. Bare 2024 has poor corrosion resistance and will pit or exfoliate in chloride environments. For saltwater or marine immersion, a 5xxx or 6xxx alloy is the safer choice; 2024 belongs in enclosed or well-coated structures.
What is the difference between 2024-T3511 and 2024-T351?
They share solution heat treatment and stretch stress relief. T3511 adds a straightening step and is assigned to extrusions (bar, tube, shape, profile); T351 is the equivalent temper for plate and sheet.
Can 2024-T3511 be anodized?
Yes. Anodizing improves surface hardness and wear resistance and gives a clean finish, but it does not replace corrosion protection in aggressive environments. Pair anodizing with paint, or use alclad stock, where exposure is severe.
What lead time should I expect for custom 2024-T3511 extrusions?
Custom non-stock extrusions typically run 10–60 days depending on alloy, dimensions, and processing requirements, with low minimum order quantities. Stock standard sizes are available for faster response, and every order includes an MTC.
