In order to promote the adoption of aluminum body panels, it is necessary to provide for the potential panel shapes and the low-cost materials required by automobile manufacturers. It is important to improve material properties as well as forming and joining technologies, so as to be able to manufacture suitable body panel shapes. On the other hand, it is necessary to minimize the number of manufacturing processes, and to be able to use recycled aluminum alloys to ensure a low-cost material.
Aluminum Alloys
The important properties required for body panels are as shown in Table 2.3. Especially, it is necessary to improve the formability to enable, for example, hem flanging and stretch-forming for outer panels, and deep drawing for inner panels. It is important to be able to decrease strength before forming, and then redevelop high strength after paint baking under conventional baking conditions.
Figure 2.3 shows a study of the bake-hardening properties of 6xxx alloys after pre-aging. The specimens are solution heat treated at a high Temperature of 530°C and then water quenched, a conventional manufacturing process for aluminum body panels. Pre-aging is conducted at 50°C to 100°C immediately after water quenching. After one week at room temperature, the specimens are then heat treated using several different baking conditions
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