The aluminum alloy main alloying elements are copper, silicon, magnesium, zinc and manganese, while the minor alloying elements are nickel, iron, titanium, chromium and lithium.

Aluminum alloy is one of the most widely used non-ferrous metal structural materials in industry. It has been widely used in aviation, aerospace, automobile, machinery manufacturing, shipping and chemical industry. With the rapid development of science and technology and industrial economy in recent years, the demand for welded structural parts of aluminium alloy is increasing day by day, which makes the research of weldability of aluminium alloy deepen. The wide application of aluminium alloys has promoted the development of welding technology of aluminium alloys. At the same time, the development of welding technology has expanded the application field of aluminium alloys. Therefore, the welding technology of aluminium alloys is becoming one of the hotspots of research.

Pure aluminium has low density (p=2.7g/m3), about 1/3 of iron, low melting point (660 C). Aluminum is face-centered cubic structure, so it has high plasticity (delta:32-40%, _:70-90%). It is easy to process and can be made into various profiles and sheets. The corrosion resistance of pure aluminium is good, but the strength of pure aluminium is very low, and the value of_b in annealing state is about 8 kgf/mM2, so it is not suitable for structural materials. Through long-term production practice and scientific experiments, people gradually strengthen aluminium by adding alloying elements and using heat treatment methods, which results in a series of aluminium alloys. The alloys formed by adding certain elements can maintain the advantages of pure aluminium, such as light weight, but also have high strength. _b values can reach 24-60 kgf/mm2, respectively. This makes its “specific strength” (ratio of strength to specific gravity_b/_) better than many alloy steels and becomes an ideal structural material. It is widely used in machinery manufacturing, transportation machinery, power machinery and aviation industry. Aircraft fuselage, skin, compressor and so on are often made of aluminum alloy to reduce self-weight. The structure weight can be reduced by more than 50% by using aluminium alloy instead of steel plate welding.

Aluminum alloy has low density but high strength, close to or over high quality steel, good plasticity, and can be processed into various profiles. It has excellent electrical conductivity, thermal conductivity and corrosion resistance. It is widely used in industry, and its usage is second only to steel.

Some aluminium alloys can obtain good mechanical properties, physical properties and corrosion resistance by heat treatment.

Aluminum alloys can be divided into two categories: cast aluminium alloys, which are used as cast, deformed aluminium alloys, which can withstand pressure processing. It can be processed into various forms and specifications of aluminium alloy. Mainly used for manufacturing aviation equipment, building doors and windows, etc.

Aluminum alloys can be divided into deformed and cast aluminium alloys according to their processing methods. Deformed aluminium alloys can be divided into non-heat-treated and heat-treated strengthened aluminium alloys. Non-heat-treatment strengthening type can not improve mechanical properties by heat treatment, but can be strengthened by cold working deformation. It mainly includes high-purity aluminum, industrial high-purity aluminum, industrial pure aluminum and rust-proof aluminum. Heat-treated reinforced aluminium alloy can improve its mechanical properties by means of quenching and aging. It can be divided into hard aluminium, forged aluminium, superhard aluminium and special aluminium alloy.

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