Dissimilar gas tungsten arc weld-brazing of Al/steel using Al-Si filler metal: Microstructure and strengthening mechanisms

• Published in: Journal of alloys and compounds 2018-06, Vol.749, p.121-127
• Main Authors: Pouranvari, M., Abbasi, M.
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum base alloys; Arc brazing; Dissimilar metals; Dissimilar welding; Filler metals; Galvanizing; Gas tungsten arc welding; Intermetallic compound; Intermetallic compounds; Iron; Joining; Low carbon steels; Silicon; Silicon steels; Steel; Welded joints; Welding; Zinc coatings; Zn-coating
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.03.224

In this paper gas tungsten arc welding (GTAW) was applied to dissimilar lap joining of Al6061 and Zn-coated galvanized low carbon steels using Al-5 wt% Si filler metal. The joining mechanism was based on a hybrid brazing/welding mechanism. Three factors contributed to the joint strength including (i) low heat input rate of GTAW process which reduce the intermetallic compound layer growth during joining, (ii) the special role of Si in the filler metal which was able to change the nature of reaction layer from predominantly η-Al5Fe2 phase to predominately less brittle Al-Fe-Si phase and (iii) the flux-like action of Zn-coating which ensures complete wetting of steel surface by Al melt. It was found that there is a critical heat input which when exceeded caused degradation of the mechanical strength of the joint due to increased intermetallic compound growth. •Dissimilar GTAW weld-brazing of Al6061 and Zn-coated low carbon steel was accomplished. .•The role of heat input on intermetallic growth and joint strength is established.•Joint strength is controlled by IMC thickness.•Si in filler metal and Zn-coating of the steel are keys in producing strong joint.