Specific Application Sites and Requirements of Aluminum Alloy materials for Aerospace

Aviation aluminum alloy is the backbone material for the manufacturing of aircraft and aerospace vehicles. With the continuous improvement of requirements for flight performance, payload, fuel consumption, service life, and safety reliability in contemporary aircraft design and manufacturing, higher and higher requirements have been put forward for the comprehensive performance and reduction effect of aluminum alloy structures. Using large-sized aluminum alloy materials for CNC milling to produce integral aluminum alloy structural components, replacing the traditional combination of multiple aluminum alloy components, can not only achieve significant weight reduction and improve the reliability of the service process, but also reduce aircraft assembly processes and manufacturing costs.

This advanced design and manufacturing method imposes very strict requirements on aluminum alloy materials: the maximum thickness of aluminum alloy forgings or pre tensioned plates often needs to reach 150mm or more, and the comprehensive performance of components with different thicknesses is highly uniform. At the same time, it also needs to have excellent strength plasticity fracture toughness fatigue resistance stress corrosion and peeling corrosion resistance matching.

Aluminum is used as the main propellant for solid rocket boosters in space shuttles due to its high volume energy density and difficulty in accidental ignition.

Aluminum alloy plates are used in a large number of aerospace applications, with complexity and performance requirements ranging from simple components to the main load-bearing structures of aircraft, such as the Airbus A340 and Boeing 777.

The aircraft and aerospace industries have long relied on aluminum alloys. If aluminum alloy is not used in the engine, the first aircraft will never be able to fly. Artificial satellites are made of aluminum, so they can survive the process of crossing our hot external atmosphere and entering space. Even today, NASA still uses aluminum lithium hybrid materials in advanced Orion spacecraft.

Whether designing commercial aircraft or constructing precision space shuttles, aluminum alloy is a crucial material. Aluminum alloy is most commonly used in the manufacturing of fuselage, wings, and support structures, bringing a series of benefits to aircraft and space flight engineering.

Aluminum alloys used in aerospace are used to handle conditions below zero temperature encountered in space cryogenic vacuum. On the other hand, aluminum alloys used in aircraft manufacturing have durability and the ability to resist various types of corrosion. The high stability of these alloys makes them an ideal choice for mechanical components, which also benefit from the high conductivity of aluminum.

The Application of Aluminum in Aviation

Aluminum is widely used in aircraft, mainly as structural components. Aluminum alloy, due to its high specific strength, good formability and processing performance, is the main structural material of aircraft, such as skin, frame, propeller, fuel tank, wall panel, and landing gear support. The aluminum conversion rate of different aircraft models can vary greatly, for example, the proportion of aluminum alloy materials in Boeing 737 can reach 81%, while the proportion of aluminum alloy materials in Boeing 787 is 20% due to the use of a large number of composite materials.

Aluminum used in aviation is mainly made of deformed aluminum, with a relatively low proportion of cast materials. On average, flat rolled materials account for about 60% of aluminum consumption in aircraft, extruded materials (pipes, rods, profiles, and wires) account for about 28%, forgings account for about 7%, and castings account for about 5%.

According to the classification of alloy composition, aviation aluminum is mainly composed of 2 series and 7 series. The aluminum alloys used for the structure of large aircraft in various countries around the world today are mainly high-strength 2 series (2024, 2224, 2324, 2424, 2524, etc.) and ultra-high strength 7 series (7075, 7475, 7050, 7150, 7055, 7085, etc.), accounting for about 38% and 45% of the proportion of aluminum materials in civil aircraft, respectively.

People have conducted in-depth and systematic research on the composition and synthesis methods, rolling/extrusion/forging/heat treatment processes, part processing, material and structural service performance characterization of aluminum alloys used in aerospace. The development of material products has formed a series, and a series of significant achievements have been made in application. Especially since the late 1980s, with the gradual formation of damage tolerance and durability design criteria for aircraft, higher requirements have been put forward for the comprehensive performance of materials such as strength, fracture toughness, corrosion resistance, and fatigue resistance. The current development direction of aluminum alloys is to develop thick plate materials with low internal stress, and a large number of thick plates are used in the manufacturing process to achieve the formation of integral structural components, replacing the components previously assembled with many parts (Figure 2). The widespread adoption of large integral wall panel structures has become an important means for the new generation of aircraft to improve structural efficiency, reduce the number of parts, lower costs, and shorten development cycles. After adopting integral reinforced wall panels on the Boeing B747 aircraft, the number of parts decreased from 129 to 7, resulting in a 25% cost reduction. The crack propagation life and residual strength were both increased by three times.

Generation one aircraft, generation one materials, aviation aluminum has developed to the third generation aluminum alloy material represented by aluminum lithium alloy. The development of aviation aluminum has three stages: the first stage was from the 1930s to the 1960s. The 2-series aluminum alloy made all metal aircraft mainstream, while the 7-series aluminum alloy represented by the early 7075 made it possible for passenger aircraft to fly in the stratosphere, with representative models being the DC-3, B-29, and 70; The second stage was from the 1960s to the 1990s, when a series of new 7-series aluminum alloys such as 7050 and 7055 were developed, which improved the specific strength while considering fatigue characteristics. Representative models were the A300 series and 777; The third stage is from 2000 to present. In the competition of composite materials, the third-generation aluminum alloys represented by aluminum lithium alloys have been increasingly adopted by new aircraft models, including A220, China's C919, etc. Representative brands are Kenlian's 2050 and 2196, as well as Alcoa's 2099 and 2397. In addition to aluminum lithium alloys, aluminum based composites and superplastic formed aluminum alloys are also key research directions for aviation aluminum.