*2.1. Materials*

Three commercial aluminum alloys AA5083-O, AA5754-H14 and AA7020-T6 were chosen for producing dissimilar friction stir butt welds. The alloys were purchased in the form of rolled plates of 10 mm thick. The butt welds were designed to be 200 mm total width which composed of two plates; each plate was 100 mm wide and 200 mm long. The nominal chemical compositions of the parent materials are listed in Table 1. Moreover, the tensile strength, temper condition and hardness of the parent materials are summarized in Table 2.

**Table 1.** Nominal chemical composition of aluminum alloys AA5083, AA5754 and AA7020.


**Table 2.** Mechanical properties of the aluminum alloys AA5083, AA5754 and AA7020.

