Abstract
Abstract The extensive use of light metal material such as aluminum has brought about problems in its joining with steel. However, the weak metallurgical bonding between the dissimilar materials and the formation of hard and brittle intermetallic compounds (IMCs) lead to unsatisfactory joint strength. Aiming at achieving high-quality joining of aluminum and steel, 6061-T6 aluminum and 301L steel alloys were lap joined by ultrasonic assisted friction stir lap welding (UaFSLW) in this study. The UaFSLW joints were well formed with uniform flashes and even arc lines. The strong plastic flow of the aluminum material driven by the dual effects of mechanical stirring and ultrasonic vibration inhibited the excessive growth of the Al–Fe IMCs at the lap interface. Thanks to the enhanced metallurgical bonding and the effective control of the layer thickness of IMCs, the tensile load of the UaFSLW joint under 1,800 rpm reached 16.5 kN, which was an increase of 27.9% compared to that of the conventional FSLW joint.
Highlights
The extensive use of light metal material such as aluminum has brought about problems in its joining with steel
According to the uneven thermalmechanical cycles experienced by materials in different zones, the upper aluminum material in the joint can be generally divided into shoulder-affected zone, pinaffected zone (PAZ), thermo-mechanically affected zone, and heat-affected zone
The violent mechanical stirring driven by the rotational tool pushes the plasticized aluminum material to downwards flow to the lap interface, which has an active effect on the interfacial joining
Summary
Abstract: The extensive use of light metal material such as aluminum has brought about problems in its joining with steel. The strong plastic flow of the aluminum material driven by the dual effects of mechanical stirring and ultrasonic vibration inhibited the excessive growth of the Al–Fe IMCs at the lap interface. It has been proved that the ultrasonic vibration can effectively improve the atomic diffusion and the material flow during welding [20], and this ultrasonic assisted friction stir lap welding (UaFSLW) technique has been successfully applied in the joining of aluminum/magnesium alloys [21] and aluminum/titanium alloys [22]. The strong plastic flow of the upper aluminum material at the interface was achieved by the dual effects of mechanical stirring and ultrasonic vibration, which aimed at improving the metallurgical bonding of dissimilar material interface, controlling the formation of Al–Fe IMCs and obtaining high-quality hybrid joint. This study is meaningful for expanding the applications of light alloy materials and the FSW technique in the industries
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