**2. Experimental Procedure**

The 6mm thick AA1050-H14 and AA5083-H111 plates were cut into 70 mm × 530 mm long strips using a guillotine cutting machine (see Figure 1).

**Figure 1.** Aluminium alloy plates prepared for welding.

The two dissimilar plates were fixed on the backplate of the semi-automated milling machine (FSW machine), as shown in Figure 2. The AA5083-H111 was kept on the retreating side throughout the experiments, while AA1050-H14 was on the advancing side. This kind of material location was followed based on the recommendation from the literature [11,12,16,19,25,26]. The plates were fixed on the machine's backplate by eight clamps. The function of clamps was to make sure the plates did not move apart when the rotating pin was in motion.

**Figure 2.** Friction stir welding machine.

The plates were then friction stir welded using a high carbon steel (H13) tool shown in Figure 3. The tool was machined using a lathe machine and was heat-treated to about 50HRC. The profile of the pin was triangularly threaded with a 20 mm shoulder diameter and 6 mm pin diameter. The triangular threaded pin had a 1mm pitch and the height of 5.8 mm. The FSW parameters used in this study are presented in Table 1, and these parameters were chosen based on various speed test combinations performed prior to the main welding. However, those trial results are not included in this work since they are not part of the paper's focus.



**Figure 3.** Friction stir welding tool.

Figure 4 shows the friction stir welding of 6 mm thick AA1050 and AA5083 plates. Stage 1 shows two plates ready for welding. Stage 2 shows the rotating tool plunged into the two pieces being welded, i.e., AA1050-H14 and AA5083-H111. Stage 3 shows the welded part of the plates. Stage 4 shows the end of FSW and the unplunging of the tool. The finished product is clearly shown in Figure 5. The nominal chemical composition for materials used in this study is presented in Table 2. The chemical composition was measured using the BELEC COMPACT PORT HLC spectrometer (Belec Spektrometrie Opto-Elektronik GmbH, Georgsmarrienhutte, Germany) according to ASTM E716-16 standard. These chemical compositions were in the range of those reported in the literature [16,21,27].


**Figure 4.** Friction stir welding process.

**Figure 5.** FSW joint.
