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Automobile, aerospace, and shipbuilding industries are looking for lightweight materials for cost effective manufacturing which demands the welding of dissimilar alloy materials. In this study, the effect of tool rotational speed, welding speed, tilt angle, and pin depth on the weld joint were investigated. Aluminum 5052 and 304 stainless-steel alloys were joined by friction stir welding in a lap configuration. The design of the experiments was based on Taguchi’s orthogonal array for conducting the experiments with four factors and three levels for each factor. The microstructural analysis showed tunnel defects, micro voids, and cracks which formed with 0° and 1.5° tilt angles. The defects were eliminated when the tilt angle increased to 2.5° and a mixed stir zone was formed with intermetallic compounds. The presence of the intermetallic compounds increased with the increase in tilt angle and pin depth which further resulted in obtaining a defect-free weld. Hooks were formed on either side of the weld zone creating a mechanical link for the joint. A Vickers hardness value of HV 635.46 was achieved in the mixed stir zone with 1000 rpm, 20 mm/min, and 4.2 mm pin depth with a tilt angle of 2.5°, which increased by three times compared to the hardness of SS 304 steel. The maximum shear strength achieved with 800 rpm, 40 mm/min, and a 4.3 mm pin depth with a tilt angle of 2.5° was 3.18 kN.

In this study, dissimilar friction stir welding of aluminum 5052 and stainless steel 304 has been carried out with different process parameters. This investigation provides a better insight regarding the defect formation of the weld joints with tilt angles ranging from 0°to 2.5°. The experiments were conducted according to Taguchi L9 orthogonal array by changing the tool rotational speed, and welding speed. The tool pin was kept 70 % towards the aluminum with the tool rotational speed ranging from 800 min À 1 to 1200 min À 1 with a varying traverse speed of 5 mm/min to 15 mm/min. The bottom part of the stir zone was perfectly welded without any defects. Tunnel defect was detected just above the bottom welded surface. Microstructural analysis reveals that the weld between both materials is formed on the retreating side, whereas on the advancing side, the weld was formed with void defects. Mostly, the stir zone is filled with irregular shaped aluminum and steel parts which were detached from the base material. Several other defects such as voids, cracks, and fragmental defects were observed in the stir zone irrespective of the process parameters. It was observed from the experimental investigations that the tunnel defect can be reduced by increasing the tilt angle.

Dissimilar material joining of aluminum and steel in the present scenario is an important criterion in the manufacturing industry, especially because of their low weight and technical performance. In the present investigation, AA5052 and SS304 are friction stir welded in lap configuration with different tilt angles, welding speed, pin depth, and tool rotational speed, with aluminum as the top plate. A maximum of 3.16 kN shear strength was achieved at 2.5° tilt angle when the penetration depth was 4.3 mm. The shear strength samples were studied for fracture analysis and it was found that fracture of the samples mainly occurred on the aluminum side and the fracture demonstrated both brittle and ductile failure, consisting of quasi-cleavage, trans-granular, and intergranular fracture areas. Field emission scanning electron microscope images at the interfacial region of the weld show that different intermetallic compounds were formed at various zones of the joint with respect to the change in process parameters. It was observed from energy dispersive spectroscopy that Al-rich intermetallic compounds were formed at the interfacial region of the welded samples. Amongst the process parameters, change in the tilt angle affected the weld zone significantly. The thickness of the intermetallic compound (IMC) layer formed with 800 and 1000 rpm at 2.5° tilt angle was between 2.5 and 3 μm, which resulted in achieving better joint strength. AlFe, AlFe3, Al13Fe4, and Al5Fe2 were the different intermetallic compounds detected using X-ray diffraction with different process parameters. The hardness of the samples ranged between (300 and 630) HV, which further supports the formation of AlFe and AlFe3 intermetallic compounds.