The Material Structure of Aluminum
Pure aluminum has a low density (ρ = 2.7 g/cm3), which is about 1/3 of iron and has a low melting point (660 ° C). Aluminum is a face-centered cubic structure, so it has a high degree of plasticity (δ: 32~40%, ψ: 70~90%). Aluminum is easy to process and can be made into various profiles and plates. Pure aluminum has good corrosion resistance. However, the strength is very low, and the annealing state σb value is about 8kgf/mm2. So it is not suitable as a structural material. Through long-term production practices and scientific experiments, people gradually strengthened aluminum by adding alloying elements and applying heat treatment, which resulted in a series of aluminum alloys. The alloy formed by adding certain elements that can have higher strength while maintaining the advantages of pure aluminum, and the σb value can reach 24 to 60 kgf/mm2, respectively. This makes its "specific strength" (ratio of strength to specific gravity σb / ρ) outperforms many alloy steels and becomes an ideal structural material. Aluminum alloys are widely used in machinery manufacturing, transportation machinery, power machinery and aviation industries. The fuselage, skin, compressor, etc. of the aircraft are often made of aluminum alloy to reduce their own weight. The use of aluminum alloy instead of steel plate welding can reduce the structural weight by more than 50%.