Process characteristics and properties of AA2219 aluminum alloy welded by double pulsed VPTIG welding

A double pulsed variable polarity tungsten inert gas (DP-VPTIG) welding process was employed in the welding fabrication of AA2219 plates. The arc profile was imaged by a high-speed camera based vision sensing system, and the weld pool appearance was captured by a CCD-based area-array camera. The microstructure, micro hardness and tensile properties of the welded joints were investigated. Results indicated that the arc length L, diameter D-B at arc workspace end and diameter D-E at arc electrode end fluctuated periodically with the low frequency pulse. In low-frequency pulse peak stage, the weld pool width D-w increased monotonously, accompanied by a significant depressed deformation on the weld pool surface. In low-frequency pulse base stage, D-w continuously decreased with the disappearance of the depressed deformation. Compared with the conventional VPTIG, the weld zone grain structure of DP-VPTIG was significantly refined, and the micro hardness and tensile properties of DP-VPTIG welded joints were improved.