Aluminum Alloys: 6061 vs 7075 vs 2024
At a Glance
Properties shown reflect the most common temper for bar and plate, the product forms we machine most frequently. All values are listed in both imperial and metric.[1]
Strength Comparison
7075 is roughly 85% stronger than 6061 in tensile strength. That difference matters enormously in structural and aerospace applications. 2024 sits in between, with its advantage showing up most in fatigue rather than peak load.[1]
Alloy-by-Alloy Breakdown
6061: The default choice
6061 is a silicon-magnesium alloy (6xxx series) and the most widely machined aluminum in the world. It offers a solid combination of strength, corrosion resistance, weldability, and machinability at a low cost.[1] In bar and plate form, you'll see it as T6511 (extruded bar, stress relieved by stretching) or T651 (plate, stress relieved by stretching). Both deliver equivalent mechanical properties to T6 sheet, with the stress relief step added to minimize distortion during machining.
Its magnesium and silicon alloying agents make it naturally resistant to corrosion, and it takes anodizing extremely well, making it the go-to for components that need a durable surface finish. It's also one of the easiest alloys to machine: it produces clean chips, holds tight tolerances without springback issues, and doesn't work-harden aggressively during cutting.[2]
7075: Maximum strength
7075 is a zinc-based alloy that sits in a different performance category entirely. Its tensile strength of 572 MPa (83 ksi) exceeds that of many structural steels, making it the aluminum of choice for aerospace structural components, aircraft frames, and high-load fixtures.[1] In machined form, 7075 plate is most commonly ordered as T651 (peak strength) or T7351 (over-aged for improved stress corrosion resistance). Bar stock typically comes as T73511.
The T73 family sacrifices roughly 10 to 15% of tensile strength compared to T6 but significantly improves resistance to stress corrosion cracking, an important consideration for parts in sustained tensile load environments.[3]
The trade-offs are real: 7075 is significantly more expensive, has poor weldability, and offers only fair bare corrosion resistance. Components often require anodize, chem film (Alodine), or clad coatings in corrosive environments.
2024: Fatigue performance
2024 is a copper-alloyed aluminum with exceptional fatigue resistance, originally developed for aircraft skins and wing structures where cyclic loading governs design life.[1] In machined form, plate is specified as T351 and bar as T3511. The T3 family is naturally aged rather than artificially aged, which gives 2024 a higher elongation (18%) and better crack propagation resistance than peak-aged alternatives.[2]
Like 7075, 2024 has poor weldability and fair bare corrosion resistance, and must be coated in corrosive environments. The copper content also makes it susceptible to galvanic corrosion when in contact with dissimilar metals, a detail that matters in assembly design.[4]
Property Comparison Chart
Toggle between properties to compare all three grades visually. Values for the most common bar/plate temper of each alloy.[1]
Full Property Comparison
All values are for the most common bar/plate temper of each alloy. Imperial values primary with metric equivalents shown.[1][2]
| Property | 6061 (T6511/T651) | 7075 (T73511/T7351) | 2024 (T3511/T351) |
|---|---|---|---|
| Ultimate tensile strength | 45 ksi310 MPa | 83 ksi572 MPa | 70 ksi483 MPa |
| Yield strength (0.2%) | 40 ksi276 MPa | 73 ksi503 MPa | 50 ksi345 MPa |
| Elongation at break | 12% | 11% | 18% |
| Fatigue strength (10⁸ cycles) | 14 ksi97 MPa | 23 ksi159 MPa | 20 ksi138 MPa |
| Elastic modulus | 10.0 Msi69.0 GPa | 10.4 Msi71.7 GPa | 10.6 Msi73.1 GPa |
| Density | 0.098 lb/in³2.71 g/cm³ | 0.102 lb/in³2.81 g/cm³ | 0.100 lb/in³2.78 g/cm³ |
| Hardness | 95 HB | 150 HB | 120 HB |
| Thermal conductivity | 167 W/m·K | 130 W/m·K | 121 W/m·K |
| Machinability | Excellent | Good | Good |
| Weldability | Good | Poor | Poor |
| Anodizing quality | Excellent | Fair | Fair |
| Corrosion resistance | Good | Fair | Fair |
| Availability | Excellent | Good | Moderate |
| Relative cost | $ (baseline) | 90$ (2-3× 6061) | 90 (1.5-2× 6061) |
Which Alloy Is Right for Your Part?
A Note on Temper Designations
When writing a drawing callout for a machined aluminum part, always specify the full temper designation for the product form you're ordering. Writing "6061-T6" on a bar-stock part is technically imprecise; the correct callout is 6061-T6511 for extruded bar or 6061-T651 for plate. Specifying the correct designation prevents ambiguity, ensures your material certifications are accurate, and matters when buying to an aerospace spec such as AMS 2770 or ASTM B209.[5]
| Temper | Description | Product forms |
|---|---|---|
| T6 | Solution heat treated and artificially aged. Peak strength, no stress relief. | SheetCoil |
| T651 | T6 + stress relieved by stretching. Standard plate temper for 6061 and 7075. | Plate |
| T6511 | T6 + stress relieved by stretching + minor straightening. Standard extruded bar/rod temper. | |
| T351 | T3 + stress relieved by stretching. Standard plate temper for 2024. | Plate |
| T3511 | T3 + stress relieved by stretching + minor straightening. Standard bar temper for 2024. | |
| T7351 | T73 + stress relieved by stretching. Preferred plate temper for 7075 where SCC resistance matters. | Plate |
Need help selecting the right aluminum alloy?
Our engineering team at C&W Manufacturing reviews material specifications as part of every quoting process. Submit your print and we'll flag any concerns before machining begins.