Aluminum alloy has low density, but relatively high strength, which is close to or exceeds high-quality steel. It has 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 aluminum alloys can be heat treated to obtain good mechanical properties, physical properties and corrosion resistance.
The hard aluminum alloy belongs to the Al-Cu-Mg system, generally contains a small amount of Mn, and can be strengthened by heat treatment. It is characterized by high hardness, but poor plasticity. Super duralumin belongs to the Al-Cu-Mg-Zn system, which can be strengthened by heat treatment, and is the aluminum alloy with the highest strength at room temperature. But the corrosion resistance is poor, and the high temperature softens quickly. Wrought aluminum alloys are mainly Al-Zn-Mg-Si alloys. Although there are many types of elements added, the content is small, so they have excellent thermoplasticity and are suitable for forging, so they are also called forged aluminum alloys.
The structure of aluminum sheet alloy
The density of pure aluminum is small (ρ=2.7g/cm3), about 1/3 of that of iron, and its melting point is low (660°C). 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, and has good corrosion resistance. However, the strength of pure aluminum is very low, and the σb value in the annealed state is about 8kgf/mm2, so it is not suitable for structural materials.
Through long-term production practice and scientific experiments, people have gradually strengthened aluminum by adding alloying elements and using heat treatment, which resulted in a series of aluminum alloys. The alloy formed by adding certain elements can have high strength while maintaining the advantages of pure aluminum such as light weight, and the σb value can reach 24-60kgf/mm2 respectively. This makes its "specific strength" (the ratio of strength to specific gravity σb/ρ) better than many alloy steels, becoming an ideal structural material, widely used in machinery manufacturing, transportation machinery, power machinery and aviation industry, etc. Aircraft fuselage , skins, compressors, etc. are often made of aluminum alloy to reduce their weight. The welding of aluminum alloy instead of steel plate material can reduce the structural weight by more than 50%.