Investigation of laser welding on butt joints of Al/steel dissimilar materials

• It was feasible to join Al/steel in butt joints using fiber laser welding.
• The mechanism of the joints was analyzed in detail.
• The thickness of IMCs layer should be controlled to obtain higher tensile strength.
• The joints failed in the FeAl3 layer, rather than the Fe2Al5 layer.

Dissimilar metals of AA6013 aluminum alloy and Q235 low-carbon steel of 2.5 mm thickness were butt joined using a 10 kW fiber laser welding system with ER4043 filler metal. The study indicates that it is feasible to join aluminum alloy to steel by butt joints when zinc layer was hot-dip galvanized at the steel’s groove face in advance, and better weld appearance can be obtained at appropriate welding parameters. The joints had dual characteristics of a welding joint on the aluminum side and a brazing joint on the steel side. The smooth Fe2Al5 layer adjacent to the steel matrix and the serrated-shape FeAl3 layer close to the weld metal were formed at the brazing interface. The overall thickness of Fe–Al intermetallic compounds layers produced in this experiment were varied from 1.8 μm to 6.2 μm at various welding parameters with laser power of 2.85–3.05 kW and wire feed speed of 5–7 m/min. The Al/steel butt joints were failed at the brazing interface during the tensile test and reached the maximum tensile strength of 120 MPa.

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