Comparing Aluminum Alloys: Find the Right Material for Your Part
Aluminum is a common and popular metal that’s used in a stunningly wide range of parts and products: automotive parts, aerospace components, boat and marine gear, consumer electronics including smart phones, industrial machinery parts, HVAC systems, the list goes on. It’s also the material most commonly requested by our customers.
Engineers and product designers frequently turn to aluminum and many of its alloys to design both prototypes and end-use parts in a variety of industries. Choosing the right aluminum alloy when designing parts is critically important because different alloys possess significantly different properties, which directly impact the part's performance, manufacturability, durability, and cost. Alloys vary in mechanical and physical properties, manufacturing/fabrication characteristics, cost, and response to the application environment.
Aluminum Alloy Properties
Aluminum has a high strength-to-weight ratio, making it lightweight, yet strong and flexible. It’s also affordable, corrosion-resistant, and works well in a multitude of applications. Most commonly, aluminum is alloyed with other elements such as silicon, magnesium, chromium, copper, zinc, and manganese.
Aluminum alloys are often used in cars because of the material’s versatility. Aluminum’s formability and corrosion resistance make it easy to work with and shape, but its structural soundness addresses the most important requirement for car bodies. Strength is important, but car bodies must be lightweight, affordable to produce, resistant to rust, and have the attractive qualities consumers seek, such as exceptional surface finishing characteristics. Aluminum nicely fits the bill.
The same holds true with aerospace parts. Aluminum alloys are often a preferred material for aerospace designs, again because of aluminum’s corrosion-resistance properties and high strength capabilities. Compared to steel, it is a lightweight option and an ideal material for a wide range of aircraft components and aerospace applications.
Lightweighting is a core need of both the automotive and aerospace industries.
With cars, lightweighting helps reduce emissions and meet improved fuel economy standards.
For aerospace, the use of aluminum alloys dramatically decreases the weight of an aircraft because it is significantly lighter than steel, allowing aircraft to either carry more weight or increase fuel efficiency. For instance, a 20% weight reduction in a Boeing 787 is expected to generate a 10–12% improvement in fuel efficiency. Along these lines, common applications in aerospace abound—many, but not all, of which, are metal: Fuel nozzles, heat exchangers, manifolds, turbo pumps, liquid and gas flow components, conformal cooling channels, fasteners, and more.
Comparing Common Aluminum Alloys
Aluminum, as a pure element, presents many desirable properties. However, by itself, aluminum might not be strong enough for a high-durability use or purpose. Accordingly, aluminum can be combined with other elements to form alloys, which are more durable and suitable for industrial applications.
And what do all of those numbers in the alloy name signify? The aluminum series names elements with four numerical digits where the first digit represents the principal alloying element, the second digit indicates a modification of a specific alloy, and the third and fourth digits are arbitrary numbers assigned to specific alloys in the series.
| Material | Process | Tensile Strength | Elongation | Hardness |
|---|---|---|---|---|
| AL 6061-T651 | CNC Milling CNC Turning Sheet Metal Fabrication |
40 ksi 276 MPa |
17% | 95 HBW 10/500 |
| Al 7075-T651 | CNC Milling CNC Turning |
83 ksi 572 MPa |
11% | 85 HBW 10/500 |
| Al 5052-H32 | Sheet Metal Fabrication | 33.34 ksi 228 MPa |
12% | 60 HBW |
| Al 5754 (Available through Protolabs Network) |
Sheet Metal Fabrication | 20-40 ksi 140-280 MPa |
≥2% | ≥50 HRB |
| Al 2024 | CNC Milling CNC Turning |
68 ksi 469 MPa |
19% | 120 HRB |
| Al (AlSi10Mg) | 3D Printing: DMLS High resolution (20 μm) |
39 ksi 268 MPa |
15% | 42 HRB |
| Al (AlSi10Mg) | 3D Printing: DMLS Normal resolution (30 μm) |
50 ksi 345 MPa |
8% | 59 HRB |
| Al (AlSi10Mg) | 3D Printing: DMLS Large Format (40 μm) |
42 ksi 296 MPa |
10% | 50 HRB |
Aluminum Materials Available Through Protolabs Factories
The most commonly used aluminum alloy at Protolabs, Al 6061 is used for CNC machining and sheet metal fabrication. It is generally selected where welding or brazing is required or for its high corrosion resistance in all tempers. Note that welding 6061 can weaken the heat-affected zone, so some post-weld treatment may be needed. It is used for automotive parts, pipelines, boat and marine gear, furniture, consumer electronics, and structural components.
This high strength alloy adds chromium to the mix to develop good stress-corrosion cracking resistance. It is the go-to alloy for aerospace parts, military applications, bicycle equipment, camping and sports gear because of its lightweight yet strong characteristics. While popular due to its strength, aluminum 7075 suffers from poor weldability and it can be quite brittle compared to some lower-strength alloys.
Often used with sheet metal fabrication, this alloy has good workability, very good corrosion resistance, high-fatigue strength, weldability, and moderate strength. This makes it perfect for use in aircraft fuel/oil lines, fuel tanks, other transportation areas, appliances and lighting, wire, and rivets.
This is a widely used, high-strength aluminum alloy with copper as the primary alloying element. Its advantages make it a go-to material for specific demanding applications, particularly in aerospace. It offers a high strength-to-weight ratio, excellent fatigue resistance, good machinability, and is heat treatable. Be aware that it has poor corrosion resistance and is not suitable for welding.
A mainstay of our 3D printing direct metal laser sintering (DMLS) process, this is comparable to the 3000 series alloy that is used in casting and die-casting processes. It has good strength-to-weight ratio, high temperature and corrosion resistance, as well as good fatigue, creep, and rupture strength. AlSi10Mg also exhibits thermal and electrical conductivity properties. Final parts built in AlSi10Mg receive stress relief application.
Aluminum Materials Available Through Protolabs Network
Aluminum 2014 is easily machined and can be hardened to get strengths comparable to steel but is prone to corrosion. Suitable for aerospace applications.
Aluminum 2017 has a higher ductility and formability than Aluminum 2014 and has intermediate strength.
Aluminum 5083 is a strain hardening aluminum alloy with excellent corrosion resistance. Suitable for marine applications. Can be welded.
Lightweight material with excellent corrosion resistance, good formability, and weldability. Suitable for automotive parts, marine components, and electronic chassis.
Alloy 6060 offers good strength, relatively good corrosion resistance and is suitable for decorative anodizing.
Aluminum 6063 has good mechanical properties and can be heat treated. Suitable for aerospace applications. Can be welded.
Aluminum 6082 has very similar composition and properties to 6061, with slightly higher tensile strength. Compliant with British Standards.
Aluminum 7050 has excellent mechanical properties with good ductility, high strength, toughness, and good resistance to fatigue. Suitable for aerospace applications.
Aluminum MIC6 is a lightweight material that can be easily machined at high speed and is free from tension, contaminants, and porosity.
Aluminum 6061 vs. Aluminum 7075
These two alloys are the most requested by our CNC machining customers so we receive a lot of questions comparing the two. Here’s how they score. The primary advantage of 7075 lies in its exceptionally high strength-to-weight ratio, significantly exceeding that of 6061, making it ideal for high-stress applications like aerospace structures and performance sporting equipment.
However, this superior strength comes with major trade-offs: 7075 exhibits poor weldability using common fusion techniques, has lower general corrosion resistance, is susceptible to stress corrosion cracking, and is typically more expensive and less ductile than 6061. In contrast, 6061 offers a more balanced profile with good strength, excellent weldability, superior corrosion resistance, better formability, and lower cost, making it a versatile workhorse alloy suitable for a vast range of general structural, marine, automotive, and consumer applications where the extreme strength of 7075 is not required.
Finishing Aluminum Parts
First, let’s look at finishing options for CNC-machined aluminum parts.
Anodizing is one of the most common finishing options, offering strong corrosion protection and enhancing the overall appearance of metal parts. Three types of aluminum anodizing are available from Protolabs:
- Chromic Acid (Type I): Provides a whisper-thin but still durable coating. Commonly used for welded parts and assemblies, and as a primer before painting. Like all anodized surfaces, it is non-conductive.
- Sulfuric Acid (Type II): Harder than Type I, it offers an exceedingly durable finish. Usage examples include carabiner hooks, flashlight handles, motorcycle parts, and hydraulic valve bodies.
- Hard Anodize or Hardcoat (Type III): This is the thickest and hardest anodize available and it has a wide range of applications for parts and products in automotive, aerospace, heavy equipment, marine, general manufacturing, and defense industries.
Another option is plating, which electrically bonds protective elements to the aluminum. Plating is available only through Protolabs Network or when you order complete prototype parts. Adding plating often means adding lead time, so keep that in mind. Also note that plating is one of the more expensive finishing options. Here’s what’s available:
| Type of Plating | Added Lead Time | |
|---|---|---|
| Anodizing | Clear anodize Type II Class 1 | None |
| Black anodize Type II Class 2 | None | |
| Red anodize Type II Class 2 | 2 days | |
| Blue anodize Type II Class 2 | 2 days | |
| Clear Chromate | Type II Class 1A | none |
| Type II Class 3 | none | |
| Yellow Chromate | Type II Class 1A | none |
| Type II Class 3 | none | |
| Type III | 2 days | |
| Nickel | Class 1 | 3 days |
| Zinc | Clear and yellow | 3 days |
| Titanium anodizing | n/a | 3days |
| Powder coating | n/a | 5 days |
| Black oxide | n/a | 5 days |
For a tough, aesthetic finish, you can choose an application of powder coating on your parts. It leaves a somewhat protective layer of polymer-based colored powder.
Interestingly, many aluminum alloys tend to be self-healing when exposed to air or oxygen. With this natural passivation process, any exposure causes the metal to form a layer of aluminum oxide on its surface, which acts as a barrier to avoid further material degradation.
Main Takeaways
Some customers ask us what the best all-purpose aluminum is. It’s a tough choice because choice of alloy is entirely predicated on what your part will be exposed to in each product. That said, many people consider aluminum 6061 to be the most well-rounded aluminum, balancing strength, corrosion resistance, weldability, and to machine or fabricate. While it costs a bit more, it offers solid performance across a range of attributes.
If cost-efficiency is your biggest concern, note that less expensive alloys may not provide the lifespan your product requires, so choose carefully, grounded in that knowledge. In terms of strength, 7075 is the strongest alloy we offer, which is why it’s often used in aerospace applications.
