In Situ SEM Observations of Fracture Behavior of Laser Welded–Brazed Al/Steel Dissimilar Joint

Journal Article · Thu Mar 15 04:00:00 EDT 2018 · Journal of Materials Engineering and Performance

DOI:https://doi.org/10.1007/S11665-018-3227-8· OSTI ID:22858020

Xia, Hongbo; Tan, Caiwang; Li, Liqun ^[1]; Ma, Ninshu ^[2]

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1. Harbin Institute of Technology, State Key Laboratory of Advanced Welding and Joining (China)
2. Osaka University, Joining and Welding Research Institute (Japan)

Laser welding–brazing of 6061-T6 aluminum alloy to DP590 dual-phase steel with Al-Si12 flux-cored filler wire was performed. The microstructure at the brazing interface was characterized. Fracture behavior was observed and analyzed by in situ scanning electron microscope. The microstructure of the brazing interface showed that inhomogeneous intermetallic compounds formed along the thickness direction, which had a great influence on the crack initiation and propagation. In the top region, the reaction layer at the interface consisted of scattered needle-like Fe(Al,Si){sub 3} and serration-shaped Fe{sub 1.8}Al{sub 7.2}Si. In the middle region, the compound at the interface was only serration-shaped Fe{sub 1.8}Al{sub 7.2}Si. In the bottom region, the interface was composed of lamellar-shaped Fe{sub 1.8}Al{sub 7.2}Si. The cracks were first detected in the bottom region and propagated from bottom to top along the interface. At the bottom region, the crack initiated and propagated along the Fe{sub 1.8}Al{sub 7.2}Si/weld seam interface during the in situ tensile test. When the crack propagated into the middle region, a deflection of crack propagation appeared. The crack first propagated along the steel/Fe{sub 1.8}Al{sub 7.2}Si interface and then moved along the weld seam until the failure of the joint. The tensile strength of the joint was 146.5 MPa. Some micro-cracks were detected at Fe(Al,Si){sub 3} and the interface between the steel substrate and Fe(Al,Si){sub 3} in the top region while the interface was still connected.

• OSTI ID: 22858020
• Journal Information: Journal of Materials Engineering and Performance, Journal Name: Journal of Materials Engineering and Performance Journal Issue: 3 Vol. 27; ISSN 1059-9495; ISSN JMEPEG
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
BRAZING
CRACK PROPAGATION
INTERMETALLIC COMPOUNDS
LASER WELDING
LAYERS
MICROSTRUCTURE
PRESSURE RANGE MEGA PA
SCANNING ELECTRON MICROSCOPY
STEELS
SUBSTRATES
TENSILE PROPERTIES
THICKNESS