Effects of welding time and alloy elements on mechanical properties of aluminum/SPCC joint using resistance spot welding

In this study, effects of welding time and elements Mg, Si and Cu in aluminum alloys on hardness and tensile shear strength of aluminum alloys/steel joints in resistance spot welding have been investigated. The welding current was kept a constant 10.5kA and electrode force was 1kN. Welding time was increased from 0.067s up to 0.2s with a rise of 0.033s. Two intermetallic compound layers were generated at weld interfacial zones between aluminum alloys and steel during welding process, and the major phases were FeAl3 adjacent and directing to aluminum alloy and Fe2Al5 adjacent and directing to the steel. Diffusion of Si in aluminum alloy occurred at the interface, whereas the diffusion of Mg and Cu was not observed at the interface according to the EPMA analysis results. Hardness of intermetallic compound layers was 13.8GPa, which was about 12 times as much as that of the aluminum alloy. The largest tensile-shear strength was obtained on the condition of 0.134 and 0.167s welding time.