**5. Effect of tool rotational speed**

To know the impact of rotational speed on FSW joints 'tensile characteristics, three distinct rotational speeds were selected to manufacture the joints. **Figure 4(a)** indicates that rotational speed affects the tensile strength of AA606l aluminum alloy of FSW joints. **Figure 5(a)** demonstrates the impact of rotational speed on AA606l aluminum alloy FSW joints impact strength. **Figure 6(a)** demonstrates the impact of AA6061

**143**

*Experimental Investigations on AA 6061 Alloy Welded Joints by Friction Stir Welding*

aluminum alloy rotational speed on FSP zone hardness. Rotational speed seems to be the most important variable of the process since it also affects the transfer speed. Higher tool rotational speed in the FSP area identified after soldering led in greater temperature and slower cooling rate. Higher rotation speed leads to excessive discharge from the top layer of the stirred materials which therefore leave voids in the FSP area. Lower heat entry situation owing to reduced rotational speed caused no stirring. As the speed of rotation rises, the stressed region expands and the place of the highest stress lastly shifts from the initial advancing side of the joint to the progressing side. This means that the position of the joint fracture is also influenced by the speed of rotation. The tensile characteristics of the joints under distinct welding circumstances led in the smallest tensile strength and ductility for a specified traverse speed at the smallest spindle speed. As the speed of the spindle increased, both power and elongation enhanced to a peak before dropping again at elevated rotational speeds. It is evident that the heat input increases in FSW as the rotational speeds increase. There are two reasons why this phenomenon can be explained: first, when a local melt happens, the coefficient of friction reduces and then reduces with heat input; secondly, some heat input is absorbed by latent heat. From this investigation, it is discovered that in the case of AA6061 aluminum alloy, the joints manufactured at a rotational speed of 2000 RPM produced better tensile strengths.

To know the impact of welding speed on FSW joints' tensile strengths, three distinct welding speeds were selected to fabricate the joints. **Figure 4(b)** indicates the impact of welding speed on AA6061 aluminum alloy FSW joints tensile strength. **Figure 5(b)** demonstrates the impact of welding speed of AA606l aluminum alloy FSW joints. **Figure 6(b)** demonstrates the impact of welding speed on AA6061 aluminum alloy FSP zone hardness. Decreased welding speed reduces the cooling ratio resulting in larger equi-axed granules in the stirring region. Poor welding speed in the FSP region resulted in sub grain coarsening. Due to the restricted moment available for regeneration, greater welding speed led in a structure with greater dislocation density. Increase in welding speed can reduce the volume of grain owing to the reduction in heat input. As a result of this exploration, it was discovered that aluminum alloy in the case of AA6061, the joints manufactured at a welding speed

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

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

*DOI: http://dx.doi.org/10.5772/intechopen.89797*

**6. Effect of welding speed**

of 72 mm/min had better tensile strengths.

applied axial force and movement of the tool pin profile.

**7. Effect of axial force**

*Experimental Investigations on AA 6061 Alloy Welded Joints by Friction Stir Welding DOI: http://dx.doi.org/10.5772/intechopen.89797*

aluminum alloy rotational speed on FSP zone hardness. Rotational speed seems to be the most important variable of the process since it also affects the transfer speed. Higher tool rotational speed in the FSP area identified after soldering led in greater temperature and slower cooling rate. Higher rotation speed leads to excessive discharge from the top layer of the stirred materials which therefore leave voids in the FSP area. Lower heat entry situation owing to reduced rotational speed caused no stirring. As the speed of rotation rises, the stressed region expands and the place of the highest stress lastly shifts from the initial advancing side of the joint to the progressing side. This means that the position of the joint fracture is also influenced by the speed of rotation. The tensile characteristics of the joints under distinct welding circumstances led in the smallest tensile strength and ductility for a specified traverse speed at the smallest spindle speed. As the speed of the spindle increased, both power and elongation enhanced to a peak before dropping again at elevated rotational speeds. It is evident that the heat input increases in FSW as the rotational speeds increase. There are two reasons why this phenomenon can be explained: first, when a local melt happens, the coefficient of friction reduces and then reduces with heat input; secondly, some heat input is absorbed by latent heat. From this investigation, it is discovered that in the case of AA6061 aluminum alloy, the joints manufactured at a rotational speed of 2000 RPM produced better tensile strengths.

## **6. Effect of welding speed**

*Aluminium Alloys and Composites*

**Figure 7.**

**Figure 8.**

**Figure 9.**

**142**

**5. Effect of tool rotational speed**

To know the impact of rotational speed on FSW joints 'tensile characteristics, three distinct rotational speeds were selected to manufacture the joints. **Figure 4(a)** indicates that rotational speed affects the tensile strength of AA606l aluminum alloy of FSW joints. **Figure 5(a)** demonstrates the impact of rotational speed on AA606l aluminum alloy FSW joints impact strength. **Figure 6(a)** demonstrates the impact of AA6061

*Effect of threaded pin profile on the microstructure of AA 6061: (a) FSP zone; (b) TMAZ; and (c) HAZ.*

*Effect of conical pin profile on the microstructure of AA 6061: (a) FSP zone; (b) TMAZ; and (c) HAZ.*

*Effect of triangular pin profile on the microstructure of AA 6061: (a) FSP zone; (b) TMAZ; and (c) HAZ.*

To know the impact of welding speed on FSW joints' tensile strengths, three distinct welding speeds were selected to fabricate the joints. **Figure 4(b)** indicates the impact of welding speed on AA6061 aluminum alloy FSW joints tensile strength. **Figure 5(b)** demonstrates the impact of welding speed of AA606l aluminum alloy FSW joints. **Figure 6(b)** demonstrates the impact of welding speed on AA6061 aluminum alloy FSP zone hardness. Decreased welding speed reduces the cooling ratio resulting in larger equi-axed granules in the stirring region. Poor welding speed in the FSP region resulted in sub grain coarsening. Due to the restricted moment available for regeneration, greater welding speed led in a structure with greater dislocation density. Increase in welding speed can reduce the volume of grain owing to the reduction in heat input. As a result of this exploration, it was discovered that aluminum alloy in the case of AA6061, the joints manufactured at a welding speed of 72 mm/min had better tensile strengths.
