Friction stir welding (FSW) of Al 6063 alloy plates of 6 mm thickness was
investigated in the present study for exploring the mechanical attributes of the
welded joints. The tool profile significantly influences the quality of joints
produced by FSW. In the current study, the influence of tool profile and FSW
process parameters on the FSW weld characteristics of similar joining of Al 6063
plates has been investigated. The effect of FSW tool rotational speed (TRS) and
tool travel speed on the FSW weld properties, mainly microstructure
characteristics, microhardness, and ultimate tensile strength (UTS), have been
studied. Comparison of two different tool profiles, namely taper and cylindrical
tool, has also been examined. The effect of transient temperature distribution
has also been studied for varying FSW process parameters.
When increasing the tool’s rotational speed from 800 to 1200 rpm at a fixed
traverse speed of 80 mm/min, a rise in peak temperature is observed. Conversely,
increasing the traverse speed from 80 to 100 mm/min while keeping the rotational
speed constant at 1200 rpm results in a decrease in the peak temperature.
Expanding the TRS from 800 to 1200 rpm—while keeping the welding speed constant
at 80 mm/min—leads to a wider FSW weld nugget zone. Under the same welding
conditions, the average microhardness of the nugget zone decreases as a result
of this increase in TRS. Additionally, as the TRS increases from 800 to 1000 rpm
at a steady traverse speed of 80 mm/min, the UTS improves and reaches a peak of
about 235 MPa, which is close to the strength of the base material. When the
rotational speed is further increased to 1200 rpm, the UTS drops to
approximately 150 MPa, likely due to overheating, which may cause grain
coarsening or softening in the welded region.
