Aviation Cast Aluminum Alloy Grade and Chemical Composition
Cast aluminum alloys are among the most important materials used in the aviation industry. With its combination of strength, lightness, and corrosion resistance, aluminum provides critical benefits to aircraft. The selection of the right aluminum alloy grade is key to providing aluminum parts that are cost-effective and meet the design requirements. Therefore, aircraft manufacturers and fabricators must have a firm grasp of the various aluminum grades and their general properties.
The alloy grade of aluminum used within the aerospace industry is typically defined by the aluminum alloy-tempering designation system developed by the Aluminum Association Inc. and approved by the Federal Aviation Administration (FAA). Alloys and their designations are referred to as alloy series, such as 2024 and 6061 and have specific properties related to their chemical composition and temper.
The most prevalent alloy-temper used in commercial aircraft and engines is 2024-T3. This alloy finding uses in structural components, wing skins, fuselage skins, and engine cowlings. In addition to 2024-T3, other commonly used alloy grades include 7075-T6, 7050-T74511-T6, 7068-T651 and 7010-T71. Examples of aluminum parts produced using these alloys include landing gear parts and bulkheads.
The two major properties of aluminum alloys are their chemical composition and temper designation. The chemical composition is composed of base metals such as silicon and aluminum, along with other elements like manganese, copper, magnesium, and zinc. These alloys have different properties due to the additional elements, such as increased strength, improved corrosion resistance, or improved heat resistance. The temper designation indicates the specific manner in which the base metal, and any additional elements, are treated to achieve the desired strength and other specific properties. The tempers can involve combinations of heat-treating, cold-working, and aging.
Each aluminum alloy grade is characterized by a distinct combination of properties, making it suitable for a particular set of effectiveness parameters. While this overview provides an understanding of the elements that go into creating an alloy, the specific range of alloy chemical composition, and temper, must be verified when selecting an alloy grade.
Table 1 provides a summary of the most popular alloy grades, along with the corresponding chemical composition and temper designation.
Table 1. Most popular aviation aluminum alloy grades
Alloy Grade Chemical Composition Temper Designation
2024 Cu 3.8-4.9%, Mg 1.2-1.8%, Mn 0.3-0.9%, Si 0.5-0.9%, Zn 0.25-0.40% T3
7075 Cu 1.2-2.0%, Mg 2.1-2.9%, Mn 0.3-0.9%, Si 0.4-1.2%, Zn 5.1-6.1% T6
7050 Cu 1.2-2.0%, Mg 2.1-2.9%, Mn 0.3-0.9%, Si 0.4-1.2%, Zn 5.1-6.1% T74511 Cu 3.5-5.5%, Mg 0.2-0.90%, Mn 0.10-0.75%, Si 0.15-1.10%, Zn 0.1-0.30% T6
7068 Cu 1.2-2.0%, Mg 2.1-2.9%, Mn 0.3-0.9%, Si 0.4-1.2%, Zn 5.1-6.1% T651
7010 Cu 1.0-2.0%, Mg 2.0-3.0%, Mn 0.25-1.0%, Si 0.4-1.2%, Zn 5.7-6.7% T71
When selecting the proper cast aluminum alloy grade for an aviation component, the chemical composition and temper designation are considered. The alloy grade must be specified according to the aluminum alloy-tempering designation system. Each of the alloy grades listed in Table 1 are common in the aerospace industry and provide a range of mechanical, corrosion, and heat resistances. With the proper selection of alloy grade and temper, aluminum aerospace components can provide superior performance.
