Effect of wire current on microstructure and properties of 7075-T6 aluminum alloy joint welded by double-wire pulsed cold metal transition method

In order to improve the performance of the fusion welded joint of 7075-T6 aluminum alloy, a double-wire pulsed cold metal transition (DW-CMTP) welding method was proposed. The effects of the average currents of double wires on the microstructure and mechanical properties of the butt joints of 7075-T6 aluminum alloy plates in 6mm thickness were studied. The results showed that in the DW-CMTP process no obvious spattering appeared and the joint was shaped very well by adjusting the leading and trailing wire currents. Both the weld penetration depth and the weld width enlarged with the increases of the average leading and trailing wire currents respectively. Increasing either the average leading or trailing wire current enlarged the bubble’s buoyant force and fostered the flow of the molten pool. The trailing wire current had a more significant effect on the reduction of porosity in the weld seam. The tensile strength of the joint increased first and then decreased with the average leading wire current increasing, while the strength decreased first and then increased with the average trailing wire current. The maximum joint strength reached 389 MPa, which was 70.8% of that of the base metal.