Aluminum alloy is mainly used as structural material in aircraft, such as skin, frame, propeller, fuel tank, siding and landing gear strut. The application and development of aluminum alloy in aerospace can be divided into several stages: in the 1950s, the main goal is to reduce weight and improve the specific stiffness and strength of the alloy; In the 1960s and 1970s, the main objective was to improve the durability and damage tolerance of alloys. The heat treatment systems of T73 and T76 of 7XXX series alloys, 7050 alloys and high purity alloys were developed. Further structural weight reduction was required in the 1980s due to rising fuel prices; Since the 1990s, the development goal of aluminum alloy is to further reduce weight, and further improve the durability and damage tolerance of the alloy. For example, a new type of aluminum alloy with high strength, toughness and corrosion resistance has been developed. A large number of complex integral structural parts are processed by thick plates instead of the parts assembled by many parts before, which can not only reduce the weight of the structure, but also ensure the stability of the performance. This can be achieved by developing thick plate materials with low internal stress.
Large extruded sections for aerospace applications
With the progress of science and technology, aluminum alloy profiles are toward large-scale, integrated, thin-wall flat wide, size of high precision, complex shape direction development, application scope has been promoted from civil materials to aerospace profiles, the main characteristics of large profiles are: (1) large-scale and integrated; (2) thin-walled and lightweight; (3) precision of section size and shape and position tolerance; (4) homogenization and excellence of the organization and properties. Because of the above characteristics of large profiles, extrusion processing has brought a series of difficulties. Aerospace large extruded profiles mainly include: integral with rib panels, I girder, wing girder, comb shaped profiles, hollow beam profiles, etc. It is mainly used as the stress structural components of aircraft, spacecraft and other aerospace aircraft, as well as the special-shaped hollow rotor girders of helicopters and airstrips.
Alloys commonly used for large extruded profiles
(1) Low strength aluminum alloy: industrial pure aluminum, 3A21, 5005, 5A02, 5A03, 5086 and other heat treatment is not strengthened, the semi-finished products in the state of annealing and cold hardening after use.
(2) Medium strength aluminum alloy is divided into two groups: heat treatment non-strengthening aluminum alloy (5A05, 5A06, 5B06) and heat treatment can strengthen aluminum alloy (6A02, 2A70, 2A06).
③ High strength aluminum alloy 7A04 and 2A12 can be sharply strengthened during heat treatment.