Experimental study on the effect of Friction Stir Spot Welding process parameters on the shear strength of created joints in AA7075-T6

In this paper, the effect of friction stir spot welding process parameters in AA 7075-T6 sheets has been investigated. Also, the effect of different rotational speeds and plunge depths of the tool with different backplate materials on shear failure load of the welding area has been studied. Joints were created in two rotational speeds of 800 and 1600 (rpm). Also, different plunge depths of 5/3, 5/5, 5/7 and 5/9 (mm) with two backplate of AA1100 and Ti6Al4V were used. Shear strength test was performed to evaluate the quality of the weld. Results indicated that the backplate material has a direct effect on the shear strength and geometry of the stir zone. In rotational speed of 1600 (rpm) and by using Ti6Al4V backplate with increasing plunge depth, upper sheet of the base metal zone has been teared. Also, it was found that high rotational speeds is caused a drop in shear strength of welds compared with low rotational speeds. Maximum load for shear failure obtained in 800 (rpm) and 5/9 (mm) with Al1100 backplate. Shear failure was observed in the joints because of propagation of crack in circumference of keyhole.