Influence of Tool Probe Profiles on the Microstructure Evolution and Mechanical Properties of Al–Zn–Mg–Cu Alloy Friction Stir Weldment

The present study aims to investigate the influence of tool profiles such as hybrid square, hybrid triangular and conventional threaded tapered on the microstructure evolution and mechanical properties of the aluminium alloys of grade AA7075-T651. The softening of the thermo mechanical affected zone/heat affected zone is the main issue, and it weakens the weldment, which in turn is detrimental to the mechanical properties. There are limited studies on the influence of tool profiles on the mechanical properties of FSW of AA7075-T651. The weld joints were fabricated with the optimised parameters using the design of experiment ANOVA analysis. The processed weldments with all three tool profiles are characterised on the ground of microstructure evolution using optical microscopy, electron back scattered diffraction and correlated with mechanical properties such as hardness and tensile test. The results conceded that the hybrid square tool profile has a maximum ultimate strength of 450.3 MPa and elongation of 7% with process parameters such as rotational speed of 1325 rpm and 120 mm/min.