Aluminum has been used for aerospace applications since the late 1800s and was even used in 1903 when the Wright brothers pioneered air flight. More recently, aluminum was used on the Apollo spacecraft, on space shuttles and within the International Space Station.
Many types of aerospace aluminum alloys are frequently used in aircraft construction due to specific metallurgic features and tolerances.
This blog takes a look at the most commonly used alloys in aerospace, why they are used, major differences and specific uses.
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Aerospace Aluminum Alloy Advantages
Aluminum has been used in aircraft for over 100 years, in space stations and space exploration because of a number of advantages.
In a general sense, Aluminum can be metallurgically described as:
- Lightweight
- Durable
- Relatively low cost
- Able to be formed and treated in technically advanced ways
- High strength-to-weight ratio
- Anti-corrosive
- Electrically conductive
- Non-sparking
- Non-magnetic
On its own, pure aluminum boasts a tensile strength of 13,000 psi. Combining aluminum with other elements creates alloys that may be stronger and/or help optimize performance in parts used for the aerospace industry.
Elements frequently combined with aluminum include:
- Silicon
- Magnesium
- Copper
- Iron
- Zinc
Further processing, such as heat treatment or cold working, can make aluminum alloys even stronger. Aluminum is approximately one-third the weight of stainless steel, more cost-effective due to its lightness, and has a better strength-to-weight ratio.
Aerospace Grade Aluminum: Types
Aluminum is classified by the use of a grading system to help engineers determine which alloy is best, based on its characteristics.
The grades most often used in the aircraft industry are:
- Aluminum 2024
- Aluminum 7075
Grades used less often, but sometimes for very specific aircraft applications include:
- Aluminum 2014
- Aluminum 2219
- Aluminum 5052
- Aluminum 6061
- Aluminum 6063
- Aluminum 7050
- Aluminum 7068
- Aluminum 7475
Differences Between Aircraft Grade Aluminum
First off, let’s compare and contrast the most widely used grades, Aluminum 2024 and Aluminum 7075 in the chart below:
| Aluminum 2024 | Aluminum 7075 | |
| Ultimate Tensile Strength | 469 MPa/68,000psi | 572MPa/83,000psi |
| Major Elements | Aluminum, Copper, Manganese, Magnesium | Aluminum, Zinc, Magnesium, Copper |
| Formability/Workability | Good | Poor |
| Weldability | Poor | Poor |
| Machinability | Fair | Fair |
| Corrosion Resistance | Poor | Average |
| Heat-Treatable | Yes | Yes |
| Strength-to-Weight Ratio | High | High |
| Fatigue Resistance | High | Good |
| Aircraft Applications | Construction of the wings and fuselage, fittings, truck wheels, hardware | Wing spar, highly-stressed structural components, fittings, shafts and gears, components of missiles |
Specific Uses of Aircraft Aluminum Grades
Aluminum alloys consistently aid in the development of specific aerospace applications. In order to understand the notable characteristics of all the aluminum alloys listed above, let’s take a look at some of their particular uses.
Aluminum 2014
Aluminum 2014 combines excellent strength with good machinability. It is easier to weld than 2024 and may be forged into aircraft parts like landing gear and hydraulic cylinders. It is also often found in the internal structure or framework of aircraft.
Aluminum 2024
In addition to what is listed in the chart above, 2024 is used in sheet forms for fuselage and wings due to its high tensile strength.
Aluminum 2219
2219 aluminum alloy boasts maximum strength at high-temperature tolerances. It was specifically used for the external fuel tank on the space shuttle Columbia.
Aluminum 5052
Alloy 5052 is the strongest non-heat-treatable aluminum alloy. It has good ductility, is weldable and has a high resistance to corrosion. It is often used to make aircraft components like fuel tanks because its properties make it so moldable and versatile, yet still quite strong.
Aluminum 6061
6061 is comparably light and is often used for lightweight applications, especially homemade kit aircraft. 6061 is welded and manipulated with ease, also making it a good option for wing and fuselage structures. When it is tempered into its 6061-T6 form it is approximately as strong as structural steel.
Aluminum 6063
Aluminum 6063 is sometimes referred to as an “architectural alloy” because it has great finishing characteristics and is often anodized to change its aesthetics. It is able to be processed through extrusion into particular shapes. It is not quite as strong as 6063, so in aerospace, it is often used for creative finishes and detail work.
Aluminum 7050
Aluminum alloy 7050 is heat-treatable and able to maintain its strength in wide plates, which makes it more resistant to fractures. It is often used in 3-6 inch thick plates that are resistant to exfoliation corrosion and stress-corrosion cracking. It is commonly used in military aircraft wing skins and fuselage.
Aluminum 7068
7068 is the strongest alloy available today, with excellent corrosion resistance. It was developed originally for ammunition applications but is also used for military aircraft that are often subject to high environmental stressors. Aluminum 7068 is found in valve bodies, connecting rods and fuel pumps.
Aluminum 7075
In addition to the general applications shown in the chart above, Aluminum 7075 was used by the Japanese Imperial Navy in its infamous World War II fighter plane, the Mitsubishi A6M. This aircraft was also referred to as “Zero” or, “Navy Type O.” Alloy 7075 is still used frequently in military aircraft; its high levels of zinc make it comparable to steel in the highest strengths, with excellent fatigue resistance.
Aluminum 7475
Alloy 7475 is derived from Aluminum 7075 and is resistant to fracture and fatigue. Its strength lends its use in fuselage bulkheads, fuselage skins and wing parts for all types of large aircraft.
Aerospace Machining Done Right
For more questions similar to, “what is aircraft-grade aluminum?”, or for information on any machinable parts, contact Moseys today.
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