This article is part of the CNC Machining Materials Guide: Metals, Plastics & Superalloys on CNX Precision.
Aluminum 2024 machining is common in aerospace shops, but this alloy deserves a careful review before you specify it. 2024 is a copper-based alloy from the 2xxx series. It offers high strength, excellent fatigue resistance, and good machinability. However, it sacrifices corrosion resistance and weldability. This guide explains when aluminum 2024 is the right choice and when another alloy fits better.
What Is Aluminum 2024?
Aluminum 2024 contains about 3.8 to 4.9 percent copper. It also holds 1.2 to 1.8 percent magnesium and 0.3 to 0.9 percent manganese. Copper gives the alloy its strength through precipitation hardening. Common tempers include T3, T351, T4, and T6. The T351 temper adds controlled stress relief, which makes thick plates stable during machining. Consequently, T351 is the standard choice for machined structural parts.
The mechanical properties explain its popularity. In the T3 or T351 temper, 2024 reaches a tensile strength near 470 MPa. Its fatigue strength is superior to most other aluminum alloys. Therefore, it suits parts that see repeated loads and vibration. Meanwhile, the alloy retains reasonable ductility for riveting and forming.
Density is about 2.78 grams per cubic centimeter, similar to 6061 and 7075. The alloy responds to solution heat treatment and natural aging. However, service temperature matters. Above roughly 150 degrees Celsius, 2024 loses strength faster than 6xxx alloys. Consequently, check the operating temperature before finalizing your material choice. Moreover, the alloy is available in many stock sizes.
Heat treatment tempers deserve a closer look. T3 and T351 are naturally aged, which delivers strength without a furnace step. T6 adds artificial aging for slightly higher yield strength. Meanwhile, the O temper is soft and easy to form. In addition, machined parts often come from T351 plate or T3 bar. Therefore, confirm the available stock form with your supplier early in the design.
Machining Aluminum 2024: What to Know
Aluminum 2024 machines very well in the annealed and T3 tempers. Chip formation is clean, and surface finishes are excellent. For example, thin webs, deep pockets, and fine threads all cut reliably. However, the alloy is not as forgiving as 6061. Residual stress in plate can cause parts to distort after heavy stock removal. As a result, rough the part, rest it, then take a final finishing pass.
- Use sharp carbide tools with polished flutes.
- Balance metal removal on both sides of the part.
- Allow the workpiece to stabilize between roughing and finishing.
- Keep the work area clean; 2024 chips are fine and abrasive.
- Check dimensions after stress relief, then machine the final features.
Coolant matters as much as cutting speed. Flood coolant controls heat and improves tool life. In addition, lubricant reduces built-up edge on the cutter. Finally, deburr promptly, because the alloy forms sharp, stringy edges that can damage fixtures and hands.
Threads deserve special attention. 2024 taps cleanly with sharp, coated taps and proper tapping fluid. For small threads, thread milling reduces tool breakage. Thin walls hold tolerances when coolant and speeds are correct. Therefore, most aerospace components machine without drama once the parameters are proven.
Surface finish is a strong point of this alloy. A light finishing pass produces a smooth, uniform appearance that suits machined aircraft parts. However, do not chase a mirror finish on thin sections. Meanwhile, chamfers and radii clean up easily with standard tooling. Moreover, the alloy accepts engraving and marking without burr problems.
Tolerances are achievable with care. Standard CNC tolerances hold on most 2024 features. However, long, thin parts need support to prevent vibration. Therefore, use a stable fixture and climb milling for fine edges. As a result, repeatability stays high across the batch.
Aluminum 2024 vs 7075 and 6061
Engineers frequently compare aluminum 2024 with 7075 and 6061. 7075 is stronger, with tensile strength near 570 MPa, but it is more expensive. 6061 is cheaper, weldable, and corrosion resistant, yet it is weaker. 2024 sits between them on strength, and it beats both in fatigue resistance. The table below shows the key differences.
| Property | 2024-T351 | 7075-T6 | 6061-T6 |
|---|---|---|---|
| Tensile strength | About 470 MPa | About 570 MPa | About 310 MPa |
| Fatigue resistance | Excellent | Good | Good |
| Corrosion resistance | Poor to fair | Good | Excellent |
| Weldability | Poor | Poor | Excellent |
| Typical use | Aircraft skins | High-stress frames | General parts |
Weldability separates the alloys immediately. 2024 is not recommended for fusion welding. Consequently, designers use mechanical fasteners, adhesive bonding, or rivets instead. 6061 welds easily, which makes it the default for fabricated frames. If your part must be welded, choose 6061 or 5083 instead of 2024.
Cost and finish also differ. 2024 costs more than 6061 but less than 7075. The alloy anodizes to a darker, warmer tint because of its copper content. For cosmetic parts, 6061 usually looks cleaner. For structural parts, the strength of 2024 justifies the price. Therefore, evaluate the total picture, not just the material cost. In addition, consider coating costs for marine exposure.
Applications of Aluminum 2024
Aluminum 2024 dominates aircraft structure. It appears in fuselage skins, wing panels, ribs, and spars. It also serves in fasteners, fittings, and helicopter components. Beyond aerospace, the alloy appears in racing parts, robotics arms, and high-performance tooling where fatigue life matters. For example, torque tubes and landing gear parts rely on 2024. Moreover, the alloy suits parts that need the highest strength-to-weight ratio among common machined grades.
Corrosion protection is essential. Bare 2024 corrodes in marine and humid environments. Anodizing, conversion coating, or cladding protects the surface. Meanwhile, sealed anodizing improves appearance. Plan the surface treatment before you finalize the design, because it affects tolerances and cost. For example, hard anodizing adds thickness, so account for it on coated features.
Quality control matters for flight parts. Material certificates verify the alloy and temper. Hardness and conductivity checks confirm heat treatment. Therefore, request test reports for critical components. A documented supplier gives you the traceability that aerospace buyers require. In addition, keep records of machining parameters for repeat orders.
Frequently Asked Questions
Is aluminum 2024 hard to machine?
No, 2024 machines well with standard carbide tooling. It cuts cleanly and holds fine details. However, residual stress can distort parts if you remove a lot of material. A stable stress-relieved temper and a balanced machining sequence solve the problem.
Why is aluminum 2024 used in aerospace?
This alloy offers an outstanding combination of high strength and fatigue resistance at low weight. Aircraft structures need those properties under repeated pressurization and flight loads. Therefore, designers choose 2024 for skins, spars, and ribs.
Can you anodize aluminum 2024?
Yes, 2024 anodizes successfully, especially in the T3 temper. Sulfuric anodizing and hard anodizing both work. However, the copper content gives the coating a darker, warmer tint than 6061. Use protective coatings whenever the part faces moisture.
Aluminum 2024 machining suits high-strength, fatigue-critical parts when you manage stress and corrosion properly. We machine this alloy for aerospace and automation clients, with stress-relieved tempers and protective finishes. Send your design to CNX Precision, and we will help you choose the right temper and coating.
For related information, see our guide to cnc machining service and 5-axis cnc machining and cnc milling vs turning and cnc machining tolerances.