Friction stir lap welding for dissimilar materials of aluminum alloy and carbon-fiber-reinforced polyetherimide

Friction stir welding (FSW) technique is considered to offer advantages in terms of dissimilar jointing. In this paper, friction stir lap welding (FSLW) for the 6061-T6 Al alloy and CFRTP are carried out to explore the bonding mechanisms of the hybrid joint. Firstly, weld surface morphology is studied with the welding parameters. Then the analyses of macro/micro-structures, mechanical tensile properties, microhardness and fractographic of the dissimilar joints are carried out by optical microscopy, scanning electron microscopy and hardness and tensile tests. Results indicate that the welding speed is the most significant factor affecting the welding surface morphology. Tensile strength reaches the maximum with the average value of 33.39 MPa at the welding speed of 180 mm/min, which is equivalent to 64% that of the parent CFRTP strength. The maximum value of 30.6 Hv is achieved at the CFRTP of the binding area when the welding speed is 180 mm / min. Microstructure analysis indicates that there are large numbers of macro- and micro-mechanical interlocks at the joint with the plasticized aluminum alloy flows into the porous structure of the pyrolysis of CFRTP resin matrix under the action of friction heat and forging force. The C content increases at the interface of Al alloy layer, which improved the mechanical properties. • Bonding mechanisms of dissimilar 6061-T6 Al alloy and carbon-fiber-reinforced polyetherimide are joined by friction stir lap welding was investigated. • Variations in the degree of intermixing are correlated with pin tool welding speed. • The strength increases first and then decreases with an increase in the tool welding speed. • Influences of welding speed parameters on weld interface surface topography and microstructure are addressed.