Microstructure and mechanical properties of laser overlap welded joints of aluminum/steel with pre-plated Cu coating

In order to study laser welding behavior of aluminum/steel dissimilar metals with pre-plated Cu coating as intermediate layer, Cu coating was electroplated on the surface of 6061 aluminum alloy and DP590 duplex steel, and laser overlap welding of 6061 aluminum alloy and DP590 dual-phase steel with pre-plated Cu coating was carried out. Microstructure and mechanical properties of welded joints were studied by scanning electron microscope, energy spectrometer, tensile experiment and microhardness experiment. The results showed that the optimized welding parameters for laser lap welding of 6061 aluminum alloy/DP590 dual-phase steel with the same thickness of 0.5 mm were that laser single pulse energy was 10 J, pulse width was 6 ms and frequency was 15 Hz. Thickness of Cu coating was 60 μm and tensile strength of aluminum/steel overlap weld was 59.8 MPa. The pre-plated Cu coating had a barrier effect, which could reduce direct diffusion of aluminum/steel, effectively inhibit formation of Fe-Al hard and brittle intermetallic compounds, improve tensile strength of the weld, and reduce microhardness of the weld. With the increase of thickness of pre-plated Cu coating, fusion interface of aluminum/steel weld became smoother.Highlights: Pulse laser welding was used for overlap welding of 6061 aluminum alloy and DP590 dual-phase steel with pre-plated Cu coating. The pre-plated Cu coating can control influence of alloying elements on quality of aluminum/steel weld and effectively improve mechanical properties of aluminum/steel overlap weld.