Pure aluminum has a low density (ρ=2.7g/cm3), about one-third of iron, and a low melting point (660 ℃). Aluminum has a face centered cubic structure, so it has high plasticity (δ: 32-40%), ψ:70~90%), Easy to process, can be made into various profiles and plates, with good corrosion resistance. However, the strength of pure aluminum is very low, and the σ b value in the annealed state is about 8kgf/mm2, so it is not suitable as a structural material. Through long-term production practice and scientific experiments, people have gradually strengthened aluminum by adding alloying elements and using heat treatment methods, which has resulted in a series of aluminum alloy spare parts. The alloy formed by adding certain elements can maintain the advantages of pure aluminum being lightweight while also having high strength, The values of σ b can reach 24-60kgf/mm2, respectively. This makes its specific strength (the ratio of strength to specific gravity σ b/ρ) superior to many alloy steels, making it an ideal structural material widely used in mechanical manufacturing, transportation machinery, power machinery, and aviation industry. Aircraft fuselage, skin, compressors, etc. are often made of aluminum alloy to reduce their own weight. Using aluminum alloy instead of steel plate material for welding can reduce structural weight by more than 50%.