The brand of
automotive grade aluminum alloys is divided into nine series from 1000 to 9000 according to the type and content of non aluminum elements.
Automotive grade aluminum alloys for automobile body mainly include: 2000 series with the highest copper content and high hardness, 5000 series mainly containing magnesium, also known as "magnesium aluminum alloy", and 6000 series with high magnesium silicon content and good corrosion resistance and oxidation resistance. Different series of plates, profiles and Aluminum alloy materials such as pipes and high-performance cast aluminum.
Skeleton part: the most stressed part of the vehicle body, which is made of 2000 series or 7000 series materials and can be strengthened by heat treatment.
Outer plate part: the secondary stress part of the vehicle body, which is made of 5000 series or 6000 series materials.
Door part: 5000 series or 6000 series materials.
Floor part: 5000 series or 6000 series materials.
Casting: high performance cast aluminum alloy, which can be strengthened by heat treatment.
Aluminum castings are made into parts that can carry large loads, which obviously reduces the weight but also has high strength. These plates have complex geometry and are usually vacuum die cast to make them have high strength. Aluminum castings also have high ductility, good welding performance and high plasticity, which ensure high safety in case of collision. The aluminum alloy type of these castings is 5000 or 6000 series aluminum alloy. At present, aluminum castings are mainly used in the structural box of electric vehicle battery pack.
Compared with cast aluminum alloys, the average application share of deformed
automotive grade aluminum alloys in automobiles is still small. According to the survey of Ducker worldwide, the deformed
automotive grade aluminum alloys accounted for only 34% of automotive aluminum alloys in 2016 (18% of rolled plates, 11% of extruded profiles and 5% of forged parts). However, on some high-end models with all aluminum body, the share of deformed
automotive grade aluminum alloys is much higher than that of cast aluminum alloy. At present, the industry has invested a lot in the R & D and application technology of deformed aluminum alloy, including all aluminum body technology, and its proportion is increasing rapidly. Ducker worldwide predicts that due to the rapid development of aluminum alloy body technology, the application of deformed aluminum alloy (especially rolled plate) in automobiles will grow rapidly (as shown in Figure 1).
Automotive grade aluminum alloys mainly include 5xxx system (Al Mg system), 6xxx system (Al Mg SI system), and a small number of 2XXX system (al CG system) and 7xxx system (Al Zn mg system). Among them, 5xxx series alloy can not be strengthened by heat treatment and has excellent forming performance, but it is easy to prolong the yield point and wrinkle the surface after forming, which affects the product appearance quality. Therefore, it is mainly used for parts with complex shapes such as inner plate. 6xxx alloy can be strengthened by heat treatment through the solid solution of Mg and Si and the aging precipitation of Mg2Si phase. After coating and drying, its strength is improved and has high dent resistance. It is suitable for parts requiring strength and rigidity such as outer plate and body frame. In addition to rolled plates, extruded profiles are also important deformed aluminum alloys for vehicles. They are generally suitable for structural parts with equal section, such as bumper, energy absorption box, front section of front longitudinal beam, threshold and rear section of rear longitudinal beam. 6xxx with medium strength is the main material of extruded profiles because of its high extrusion rate, surface quality and age hardening characteristics in the extrusion process. In some occasions with high strength requirements, high-strength 7xxx aluminum alloy is also used to produce extruded profiles.
