Microstructure and Properties of Resistance Element Welded Joints of DP780 Steel and 6061 Aluminum Alloy

• Published in: Metals (Basel ) Vol. 15; no. 3; p. 283
• Main Authors: Wu, Qinglong, Yang, Yue, Li, Yingzhe, Guo, Qing, Luo, Shuyue, Luo, Zhen
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2025
• Subjects: Alloys; Aluminum; aluminum alloy; Aluminum alloys; Aluminum base alloys; Automobile industry; Dissimilar material joining; Dissimilar metals; DP780 steel; Dual phase steels; Electrodes; Electron back scatter; Electron probe microanalysis; failure mode; Failure modes; High strength steels; Intermetallic compounds; Investigations; Martensite; Mechanical properties; Microhardness; Microstructure; Morphology; resistance element welding; Solidification; Specialty metals industry; Spectrum analysis; Steel; Thickness; Welded joints; Welding; Welding current; China; Japan
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met15030283

This study developed a metallurgical and mechanical hybrid resistance element welding (REW) method to fabricate lightweight Al/steel joints between 2.0 mm 6061 aluminum alloy and 1.2 mm DP780 steel, addressing critical challenges of interfacial intermetallic compounds (IMC layer thickness: 4.6–8.3 μm) in dissimilar metal welding. In addition, the scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and electron probe microanalysis (EPMA) were used to observe the microstructure characteristics and element distribution. The lath martensite and solidification microstructure were observed in the steel-nugget zone and Al-nugget zone, respectively. Furthermore, the microhardness distribution, volume fraction of the α phase, tensile–shear load, and failure mode of REWed joint were studied. Process optimization demonstrated welding current’s pivotal role in joint performance, achieving a maximum tensile–shear load of 6914.1 N under 10 kA conditions with a button pull-out failure (BPF) mechanism.