*2.2. Creep Age Forming Experiments*

The 360 mm × 220 mm × 4 mm 7075 aluminum alloy plates were prepared by wire electrical discharge machining (WEDM). The solid solution treatment was carried out at 753 K for 0.5 h in a chamber type electric resistance furnace (SX-12-10, Beijing Ever Bright Medical Treatment Instrment Co., LTD., Beijing, China) and was immediately followed by quenching in water (298 K). The transfer time from the furnace to the water was less than 5 s.

The creep age forming experiment was conducted in an electro thermostatic blast oven (Shanghai Jing Hong Laboratory Instrument Co., LTD., Shanghai, China) which has a temperature accuracy of 0.1 K. The experiment rig is shown in Figure 1. The creep age forming experiment process includes three steps: (1) prebending—placing the 7075 aluminum alloy plate in the center of the mold, with a threaded rod and nut used to apply the prebending load, as shown in Figure 1a; (2) aging—the 7075 aluminum alloy plate was aged at 443 K for 10 h in the electro thermostatic blast oven, as shown in Figure 1b; (3) unloading—removing the load and temperature after aging, the formed aluminum alloy plate was obtained after springback, as shown in Figure 1c. The experiment was divided into three groups, with the prebending radius ρ<sup>1</sup> = 500 mm, ρ<sup>2</sup> = 1000 mm, and ρ<sup>3</sup> = 1500 mm, respectively. In order to improve the credibility of the experiment, each group of experiments was carried out three times. The specific process parameters of the experiments are shown in Table 1.

**Figure 1.** Creep age forming experiment: (**a**) prebending, (**b**) aging, and (**c**) unloading.

**Table 1.** The parameters of the experiments.

