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 DB at arc workspace end and diameter DE at arc electrode end fluctuated periodically with the low-frequency pulse. In low-frequency pulse peak stage, the weld pool width Dw increased monotonously, accompanied by a significant depressed deformation on the weld pool surface. In low-frequency pulse base stage, Dw 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.