Microstructure and mechanical properties of aluminium alloy 7A52 thick plates welded by robotic double-sided coaxial GTAW process

The high strength aluminium alloy 7A52 thick plate is commonly welded by double-V butt welding. The general one sided arc welding requires indispensable root cleaning before the rear side root weld, which consumes excessive time and cost. Thus the robotic welding is always difficult to be carried on. In this paper, a novel robotic double-sided coaxial GTAW process has been applied to the welding of Al7A52. The microstructure and mechanical properties of the thick weld joints both welded by robotic self-fluxing double sided coaxial GTAW (RSF-DSC-GTAW) and robotic wire-feed double sided coaxial GTAW (RWF-DSC-GTAW) has been investigated. It was found that the microstructures of weld zones of both processes typically consist of α (Al) and β (MgZn2) phases. Moreover, the weld zone of the RWF-DSC-GTAW joint exhibits Interval layers distribution because of the less proportion of β phase. The average micro hardness in the weld zone of RSF-DSC-GTAW joints and RWF-DSC-GTAW joints are 91.9 HV and 80.1 HV, respectively. With a better elongation property, the average ultimate tensile strength of RSF-DSC-GTAW joint is 344 Mpa. While it is 244 Mpa for the RWF-DSC-GTAW joint. It is considered that the mechanical properties of the RSF-DSC-GTAW joint are more superior to the RWF-DS-GTAW joint.