Aluminum has an extensive and successful history in the aerospace sector. As far back as the 19th century, Count Ferdinand Zeppelin used this material to create the frames of his iconic airships. Aluminum was selected because it is strong, lightweight (approximately 70% lighter than steel), and has high corrosion resistance. This article examines some common alloys employed in aerospace engineering and their applications, as well as some less popular ones, and what the future holds for aerospace materials.
A Brief History
In 1903, the Wright brothers selected aluminum for the cylinder block and other engine components for their first manned flight. It was the first time an aluminum alloy been heat-toughened. This finding resulted in the extensive use of aluminum in aerospace engineering.
Over the years, the aerospace sector has become more challenging in what it requires from materials. The arrival of long-haul international flights and gigantic jets meant that the shell and engine components had to be greatly durable and resistant to fatigue. This has resulted in the development and use of various types of aluminum alloys.
Commonly Used Aluminum Alloys in the Aerospace Industry
AA 2014 is second only to 2024 with regards to its popularity in aerospace engineering. It is a hard and strong metal, and is appropriate for arc and resistance welding. Conversely, it has poor resistance to corrosion and as a result it is frequently found in the framework or internal structure of aircraft rather than the shell.
Aluminum alloy 2024 is perhaps the most extensively used alloy for aircraft. It was developed after several experiments enabling small quantities of cold deformation, and a period of natural aging resulted in an increased yield strength. 2024 is a high-grade aluminum alloy and has good fatigue resistance. It is used mainly in sheet forms such as for the wings and fuselage owing to its high tensile strength of approximately 470 MPa.
Among the non-heat treatable alloy grades, 5052 is highly ductile and offers the highest strength, and hence it can be modeled into many different shapes including fittings and engine components. It also has high resistance to corrosion.
The 6061 alloy is very common in light aircraft, particularly homemade ones. It can be easily welded and altered, and is extremely lightweight and relatively strong which make it perfect for wings and fuselage.
This alloy maintains strength in broad segments and has high corrosion resistance. As a result, it is more resistant to fractures when compared to other alloys. It is usually employed in fuselage and wing skins, particularly in military aircraft.
AA 7068 is the strongest alloy available at present. Its low mass makes it ideal for military aircraft that need to withstand difficult conditions and attacks.
AA 7075 has excellent fatigue resistance and has similar strength properties like steel because of its high levels of Zinc. The alloy can be machined easily and hence it was highly preferred for fighter planes in World War II, including the Mitsubishi A6M Zero fighter used by the Japanese Imperial Navy on their carriers between 1940 and 1945. Even to this day, the 7075 alloy is still used frequently in military aircraft.
Typical Mechanical Properties of Some Commonly Used Aerospace Aluminum Alloys
||Elastic Modulus (GPa)
||Yield Strength (MPa)
||Tensile Strength (MPa)
||Fracture toughness (MPa√m)
Source: Aerospace Materials and Material Technologies. Volume 1: Aerospace Materials. Indian Institute of Metals Series. N. Eswara Prasad, R. J. H. Wanhill. Springer Singapore.
Less Common Aluminum Alloys in the Aerospace Industry
AA 2219 is the best option if one requires an aluminum alloy that offers maximum strength at elevated temperatures. This alloy was used for the external fuel tank of the first successfully launched space shuttle, Columbia. Although it has good weldability, the welds have to be heat-treated to maintain resistance against corrosion.
This alloy is mainly used for architectural and aesthetic finishes. One can find 6063 aluminum in the finer details of an aircraft, as it is mainly employed for intricate extrusions.
AA 7475 has high fatigue and fracture resistance. Due to its toughness, this alloy is occasionally found in fuselage bulkheads of larger aircraft.
The Future of Aluminum Alloys in Aerospace
Industry specialists are confident about the future of aluminum alloys in aerospace. It is predicted that demand for aluminum will double in the next 10 years, and there will be a global demand of 80 million tons by 2025. Consequently, the aerospace industry is increasingly considering recycled alloys in order to meet their high demand. There is also a push for the design structure of aircraft, as well as innovation in the materials used.
For example, aluminum-lithium alloys have been made for the aerospace industry to decrease the aircraft weight and thus enhance the performance of the aircraft. Al-Lithium alloys are advanced materials due to their high specific modulus, low density, and excellent fatigue and cryogenic toughness properties.
Over the years, there will be more innovation in aluminum alloys as developing countries become increasingly involved in the aerospace industry, with increased capital.
This information has been sourced, reviewed and adapted from materials provided by Matmatch.
For more information on this source, please visit Matmatch.