**7. Effect of axial force**

In order to understand the impact of axial force on the tensile strengths of FSW joints, three distinct axial forces were selected to fabricate the joints. **Figure 4(c)** shows the axial force impact on the tensile strength of the FSW AA 6061 aluminum joints. **Figure 5(c)** shows the axial force effect of FSW aluminum joints AA 6061. The **Figure 6(c)** demonstrates the axial force impact of AA6061 aluminum alloy FSP zone hardness. The flow of materials within the weld area is affected by an extrusion method where the material has experienced plastic deformation by the applied axial force and movement of the tool pin profile.

The difference in the measured forces is due to the decrease of the material flow stress at elevated weld temperature. Despite the fact that weld joint is great, the arrangement of shear lips or flashes with intemperate stature on both progressing and withdrawing sides of the weld line because of higher pivotal power brought about inordinate diminishing of the metal in the weld region yielding poor tensile properties. The axial force should therefore, be optimized in order to achieve an FSP region that is metal consolidated and does not dilute the base material. The results of this research showed that in the event of AA6061 aluminum alloy, the joints made with an axial force of 2 KN had better tensile strengths. **Table 4** shows the optimized welding conditions.
