Today’s aircrafts are built largely with aluminum alloys.
On average, aluminum accounts for 80% of the weight of a commercial aircraft and most of the fuselage, wing, and supporting structures have been built with aluminum alloys. Aluminum alloys are chemical compositions in which elements like zinc, copper, iron, manganese, or silicon, have been added to aluminum to enhance properties like corrosion resistance, electrical conductivity, or strength.
“There are many aluminum alloys that are used for many different purposes,” said Jamie Barron, Vice President of New Source Corporation. “The same aluminum extrusions may even be available in multiple different alloys.”
Alloys have four-digit numbers that begin with a digit that represents a general class, or series, characterized by its main alloying elements. Though there are 531 aluminum alloys with more being developed on a consistent basis, a quality supplier of aluminum aircraft extrusions can help a manufacturer choose the right alloy based on how it will be used.
For example, New Source Corporation keeps as much stock of aircraft extrusions made from the common aluminum alloys for aerospace as possible and helps manufacturers find the right part and get it quickly. New Source Corporation most commonly fills orders for the following alloys.
Copper is the main alloying element in the 2xxx series of aluminum alloys. 2024 aluminum is widely used for the high strength that comes from solution heat treating.
In solution heat treating, an alloy is heated to a specific temperature so that elements, in this case, copper and aluminum, mix. Then the metal is cooled in a solution that keeps the elements together. The alloy’s strength is then increased through an “aging” process in which the compounds created through heat treatment bond with the aluminum’s microstructure.
There are different types of 2024 aluminum. The designations of the different 2024 aluminum alloys denote their “tempers,” which are based on how they were heat treated and aged.
With tempered 2024 aluminum, a “T” follows the alloy number. Then a digit that indicates the heat treatment method comes after the “T.” Additional numbers may follow that first digit to convey manufacturing qualities. For example, in temper 2024-T42, the “4” means the alloy is strengthened with solution heat-treating and natural aging while the “2” signals that a buyer needs to heat-treat the metal.
Known for high strength, good workability, and excellent machinability, 2024 aluminum is commonly used in structural aircraft parts, according to Thomasnet.com. Cladding it can make it resist corrosion as well.
Silicon and magnesium are the primary alloying elements in the 6xxx series of aluminum alloys. The digit that follows the “6” in this series indicates the degree of impurity control for the base aluminum, with “0” signifying that the alloy is mostly commercial aluminum with its existing impurity levels and that controls do not need to be tightened. The third and fourth digits in a 6xxx series represent individual alloys.
6061 aluminum is easily formed, weldable, good at resisting corrosion, and heat treatable, according to Thomasnet.com. Its mechanical properties differ according to its heat-treatment method.
Values measure the alloy’s resistance to deformation, which is also known as its “stiffness.” Generally, this alloy is easy to join via welding and readily deforms into most desired shapes, making it a versatile manufacturing material,” Thomasnet.com says.
6061 aluminum tempers vary in the following types of strength.
- Yield strength – Amount of stress needed to deform the part elastically
- Ultimate strength – How much stress the alloy can take without fracturing
- Shear strength – Resistance to being sheared by opposing forces
- Fatigue strength – Ability to handle a small load repeatedly
6061 aluminum is used for its corrosion resistance as well. Together with its high strength, 6061 aluminum’s corrosion resistance makes the alloy a common choice for materials used in building aircraft frames, according to Thomasnet.com.
One of the most common types is 6061-T6 aluminum, which is formed by using high temperatures to increase the yield strength of aluminum through a process known as “precipitation hardening.” Its hardness and durability are increased.
Zinc is the primary alloying element in the 7xxx series of aluminum alloys. Magnesium, chromium, and copper also may be used. The 7xxx series of alloys are heat-treatable and have very high strengths.
7075-T6 aluminum is also very machineable and has a low density. It is often used for structural parts that are highly stressed.
The “T6” temper indicates that the alloy has been treated with solution heat to produce an alloy with peak strength. Comparable in strength to steel, it also resists corrosion and is often used by aerospace manufacturers due to its favorable strength-to-weight ratio.
These are just some of the common aluminum alloys for aerospace. More are available for aluminum aerospace extrusions.
“We carry multiple alloys for many parts so that aerospace manufacturers can get the part they need,” Barron said. “And, if we don’t have a part in stock, we can quickly get it from a partnering manufacturer so that our customers can get everything they need from us.”