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    Mechanical properties and corrosion behavior of similar/dissimilar resistance spot welded automotive aluminum alloysMechanische Eigenschaften und Korrosionsverhalten von artgleichen/artungleichen widerstandspunktgeschweißten Aluminiumlegierungen für die Automobilindustrie
    (Wiley-V C H Verlag Gmbh, 2023) Kaya, I.; Baser, T. A.; Kahraman, N.
    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. In this work, AA5754 H111-AA6063 T4 materials were joined both similarly and dissimilarly by resistance spot welding method. A mid-frequency direct current technology was used instead of conventional alternative current (AC) technology. The welded zones were examined by micro hardness measurements, microstructural characterization, tensile-shear, cross-tension and salt spray corrosion tests.image
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    MICROSTRUCTURE AND MECHANICAL PROPERTIES OF DISSIMILAR RESISTANCE SPOT WELDED ZN-COATED DP800-TBF1180 AUTOMOTIVE STEELS USING MFDC TECHNOLOGY
    (Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2024) Hidiroglu, M.; Baser, T. A.; Kahraman, N.
    The use of advanced high-strength steel in the automotive industry is increasing in last decade. This is due to the restrictions to reduce fuel consumption and thereby decrease harmful carbon dioxide emissions. This paper aims to investigate welding properties of dissimilar resistance spot welded hot dip galvanized DP800-TBF1180 automotive steels using MFDC (Mid Frequency Direct Current) technology. LME crack occurrence due to the zinc coating was determined by magnetic particle test. The mechanical properties of welded joints were determined by tensile-shear, cross-tension and hardness measurements. The micro structural characterization was also performed in the weld zones of the joints. The appropriate welding parameter range were selected for welding processes by MFDC technology. Therefore, LME crack formation were not observed according to magnetic particle test. The highest strength was obtained as 17.60 kN and 5.51 kN by tensile-shear and cross tension tests, respectively with a welding current of 8 kA. In addition, a soft zone was found in the HAZ for both base metals. The hardness decrease in HAZ is more pronounced on the TBF1180 side. The soft zone hardness values of the sample S4 were approximately 330 HV, and the hardness values of the base material were measured in the range of 376-386 HV.