After a long period of development, the most common automotive aluminum sheets are 5000 (Al-Mg) series, 6000(Al-Mg-Si) series and 7000((Al-Zn-Mg-Cu) series. Among them, the alloys that can be strengthened by heat treatment are 6000 and 7000 alloys, and the 5000 alloys are non-heat-treatable alloys.
The main alloying elements of 6000 series are Mg and Si elements, and the main strengthening phase formed is Mg2Si phase, which is an alloy that can be strengthened by heat treatment. The popular alloy grades are Al6016, 6111, 6061, 6010, 6009, etc.
6000 aluminum alloys have good formability. Although the 6000 series plates may crack at the edge during actual production and processing, considering the recovery cost, 6000 aluminum sheets have excellent comprehensive properties and are most likely to become such all-round alloy plates.
The 7000 aluminum alloys mainly contain Zn, Mg, and Cu as the main alloying elements, and the main strengthening phase is the η (MgZn2) phase, which is also an alloy that can be strengthened by heat treatment. The η phase has the characteristics of fine and dispersed distribution, and the alloy contains a higher fraction of precipitated phases, which makes the strength of the 7000 series significantly higher than that of other series.
The development of 7000 series has gone through four stages: the first stage is to develop alloys with high strength and low toughness; the second stage changes the aging process, improves the corrosion resistance of the alloy, and gets a high-strength corrosion-resistant alloy.
In the third stage, through the adjustment of the alloy composition, the toughness of the alloy is improved to form a high-strength, high-toughness and corrosion-resistant alloy; in the fourth stage, the overall performance of the alloy is improved synergistically, and an ultra-high-strength, high-toughness and corrosion-resistant alloy is formed.
5000 aluminum alloy is an alloy series with Mg as the main element. Through heat treatment, the alloy cannot be strengthened, but the distribution of precipitated phases can be changed, thereby improving the corrosion resistance of the alloy. The main strengthening modes of this alloy are solid solution strengthening and work hardening. The common alloy grades are 5182, 5052 and 5754 aluminium alloy.
Compared with other grades, 5000 aluminum alloys have the advantages of low density, high specific strength, good formability and welding performance. When applied to automobile panels, the formability of 5000 series aluminum alloys is better than that of other series of aluminum alloys.
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