Experimental investigation on microstructural and mechanical properties of in situ SiC-reinforced friction stir spot weld of Al 6061-T6

Friction stir spot welding on Al 6061-T6 aluminium alloy was performed to examine the influence of parameters, e.g. tool pin profile, shoulder plunge depth, diameter of shoulder and SiC particles on mechanical properties, macro-structural and micro-structural properties of welds. During the detailed experimentation the behaviour of hook formation, stir zone width, bonded region width and tensile-shear strength was scientifically measured, studied and discussed. Distribution of SiC particles was analysed as it affected the weld quality. Homogeneous distribution of SiC particles helped in entrapping the dislocations during tensile-shear loading of welds. A stronger weld was witnessed with the increase in diameter of the tool shoulder, while there was an increase and then a sudden decrease in weld strength with increase in shoulder plunge depth. Square tool pin was identified as optimum tool pin profile for obtaining stronger welds. The reduction in hook formation was observed with increased shoulder diameter and shoulder plunge depth. Square tool pin increased the material flow and reduced hook length by pushing it away from key hole due to increased stir zone width. SiC particles were observed to be homogeneously distributed with square tool pin profile, greater diameter of tool shoulder and optimum shoulder plunge depth.