HF pulse effect on microstructure and properties of AC TIG butt-welded joint of 6061Al alloy

Butt joint welding of 6mm thickness of 6061 aluminum alloy was used to characterize the high frequency (HF) pulse modulated square wave AC TIG (HFPM AC TIG) welding with filler wire addition. The heat input required for achieving fully penetrated weld is remarkably reduced by the modulation HF pulse. The weld penetration is increased and weld width is decreased at the same equivalent current. The width of partially melted zone, dissolution zone and overaged zone are all decreased. The formation of columnar grain around the fusion line is suppressed and the formation of the equiaxed grain is promoted. The number density and average size of micropores in weld metal are greatly reduced. The softening effect of welding thermal cycle is significantly relieved. The strength and elongation of the welded joint are increased by 8.5 % and 19.8 % respectively, and the strength and elongation of the weld metal are increased by 6.1 % and 46.1 % respectively.