*2.3. Specimen Preparation*

After the creep age forming experiments, the tensile and HCF specimens of 7075 aluminum alloy were machined by WEDM along with the direction *x* (the rolling direction), *y* (the vertical rolling direction) and *z* (the thickness direction), as shown in Figure 2a. The shape and size of the specimens are shown in Figure 2b,c, respectively. Meanwhile, several specimens were machined for hardness testing and microstructure observations. All the specimen surfaces were polished using fine sand paper (1500 #) and rinsed with alcohol before testing.

**Figure 2.** Size of the specimens: (**a**) cutting direction, (**b**) high cycle fatigue (HCF) specimen, and (**c**) tensile specimen (unit: mm).
