Mechanical properties and corrosion behavior of similar/dissimilar resistance spot welded automotive aluminum alloys

Recently, usage of high strength aluminum alloys in automotive applications increase. The reasons for that increase are the light‐weight, high strength, good formability, weldability and corrosion resistance of the aluminum alloys to improve fuel economy as well as decreasing carbon dioxide emission. Automotive hybrid structures are commonly manufactured using dissimilar AA5000‐AA6000 joints to improve mechanical requirements and corrosion resistance of the parts. In this study, AA5754 H111‐AA6063 T4 materials were joined both similarly and dissimilarly by resistance spot welding method. Within the study, a mid‐frequency direct current technology was used instead of conventional alternative current technology. The welded zone was investigated by micro hardness measurements and microstructural characterization. Tensile‐shear and cross‐tension tests were performed. The welded zone of all welded specimens was subjected to salt spray corrosion test. A nugget pull‐out fracture mode was observed on the fracture surface of the all welded joints after tensile‐shear and cross‐tension tests. The lowest hardness values were measured from the weld metals for all welded joints. Porosity and inclusion were observed in the weld nugget with minor cracks in heat affected zone by optical microscope investigations.