*4.2. Tensile Test*

Figure 10 shows the fractured specimens post tensile tests. It was observed that the fracture occurred on the advancing side (AA1050) of the specimen. This behaviour suggests that the weld joint was mechanically stronger than the AA1050 alloy [11,12,28]. This also suggests that the welded joint was dominated by AA5083-H111, hence it was stronger [16,29–31].

**Figure 10.** Fractured specimens.

Table 3 shows the results of the ultimate tensile stress (UTS) and percentage elongation. The AA1050 and AA5083 show the UTS of 104.89 MPa and 326.75 MPa, respectively, while the FSW specimens A, B, and C show 50.67 MPa, 66.47 MPa, and 63.19 MPa, respectively. It should be noted that all the specimens were fractured by the HAZ region of the AA1050-H14 side. The HAZ region is known to have a negative impact towards the UTS of a material due to the coarsened grains that are normally associated with this region [19,20,30–33]. This is suggested to be the cause of the lower UTS for the three specimens compared to the parent materials. This assumption is in line with the grain variations observed during microstructural analysis. The percentage elongation was found to be 19%, 25%, and 26% for specimen A, B, and C, respectively. These indicate that the FSW specimens B and C were more ductile compared to the specimen A and AA1050-H14 parent material, but less ductile compared to parent material AA5083.



Figure 11 shows the tensile test-strain curve of AA1050-H14, AA5083, and FSW specimens A, B, and C. The UTS of the parent material AA5083 was larger than that of the parent material AA1050-H14 and of the FSW specimens. Specimen A, which was the first specimen from the welded plate, was the weakest while specimens B and C were close to each other. This behaviour was assumed to be caused by insufficient heat input at the beginning of the weld. The temperature stabilized from the middle to the end of the plate, hence improved UTS.

**Figure 11.** Stress-strain curve.
