The density of pure aluminum is small (ρ=2.7g/cm3), which is about 1/3 of that of iron. Its melting point is low (660°C). Aluminum is 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, plates, and has good corrosion resistance. However, the strength of pure aluminum is very low, and the annealing state σb value is about 8 kgf/mm2, so it is not suitable as a structural material. Through long-term production practices and scientific experiments, people have gradually strengthened aluminum by adding alloying elements and using heat treatment methods. This has led to a series of aluminum alloys. The alloy formed by adding certain elements can maintain high strength while maintaining the advantages of pure aluminum, and the σb values can reach 24 to 60 kgf/mm2. This makes its “specific strength” (the ratio of strength to specific gravity σb/ρ) outweigh many alloy steels and becomes an ideal structural material. It is widely used in machinery manufacturing, transportation machinery, power machinery and aerospace industries, etc. , skin, compressors, etc. are often made of aluminum alloys to reduce their own weight. The use of aluminum alloy instead of steel plate welding can reduce the structural weight by more than 50%.

Aluminum alloy has low density, but high strength, close to or more than high-quality steel, good plasticity, can be processed into a variety of profiles, has excellent electrical conductivity, thermal conductivity and corrosion resistance, widely used in industry, the amount of use is second only to steel . Some aluminum alloys can be heat treated to obtain good mechanical properties, physical properties, and corrosion resistance. Hard aluminum alloy is AI-Cu-Mg system, generally contains a small amount of Mn, heat treatment can be strengthened. It is characterized by high hardness but poor plasticity. Super hard aluminum belongs to the Al-Cu-Mg-Zn series, heat-treatable, is the highest strength aluminum alloy at room temperature, but poor corrosion resistance, high temperature softening faster. The wrought aluminum alloy is mainly an Al—Zn—Mg—Si alloy. Although there are many kinds of added elements, the content is small, so it has excellent thermo plasticity and is suitable for forging, so it is also called forged aluminum alloy.