Optimization of weldability and joint strength of Al-Mg-Si with additional Al-Si cladding based on a design of experiments investigation

Some aluminum alloys, such as those alloyed with Si and Mg, are difficult to weld due to their susceptibility to hot cracking. Previous research has investigated this challenge in resistance spot welding (RSW). To improve the weldability of the AW-6111 aluminum alloy, the roll cladding process was employed, combining it with AW-4045 as the cladding material. This resulted in a wider weld lobe, improved electrode wear, and enhanced joint quality. However, it is evident that the cladded material could benefit from improved welding conditions. Despite a larger nugget diameter, similar mechanical properties were observed for both the minimum and maximum boundary conditions of the weld lobe, determined by I_nom and I_max.

This study employed a design of experiments approach to optimize the joint strength and improve the weld quality of the AW-6111 + AW-4045 cladded sheets. The tensile-shear test results demonstrated an improvement in lap-shear strength of 38 % and 44 % compared with the previous study. Furthermore, the test samples predominantly exhibited a ductile partial thickness failure mode, and a significant improvement in the weld nugget quality of the cladded AW-6111 + AW-4045 was observed. The cladded joints also exhibited a Si alloying content of approximately 5 % in the heat-affected zone and fusion zone, thereby reducing the risk of crack formation and propagation, thus improving significantly the weld quality. The results of this study contribute with the continuous validation of Al alloys for the transport industry and with the use of cladding technology to enhance the aluminum sheet properties and respective weld quality.