Friction spot extrusion welding on dissimilar materials AA2024-T3 to AA5754-O: effect of shoulder plunge depth

In the present investigation, friction spot extrusion welding was investigated for dissimilar AA2024-T3 and AA5754-O materials, under the effect of three different shoulder plunge depths of 0.25, 0.35 and 0.45 mm, keeping other parameters constant. The welded specimens were evaluated by visual inspection, optical microscopy, scanning electron microscopy, electron backscattered diffractions, and tensile testing. The results revealed that the effective metallurgical bonding and mechanical locking were obtained in case of weld produced by plunge depth of 0.45 mm. The metallurgical bonding is obtained between extruded material and surfaces of predrilled cavity, whereas mechanical locking is obtained through filling an extruded material in the predrilled cavity. The plunge depth variations influence the grain structures of processed zones. Increased plunge depth of 0.45 mm results in effective materials mixing with zigzag pattern of oxide layer mixed in the stir zone. In case of weld produced by plunge depth of 0.25 mm, the oxide layer was found as separating layer between workpieces. The weld produced by maximum plunge depth of 0.45 mm was resulted to higher fracture load of 5198 N. Trans-granular ductile fracture was observed for weld produced by plunge depth of 0.45 mm.