High-frequency pulse-modulated square wave AC TIG welding of AA6061-T6 aluminum alloy

Abstract

Bead-on-plate welding of 6-mm thick AA6061-T6 aluminum alloy is used to characterize the high-frequency (HF) pulse-modulated square wave AC TIG (HFPM AC TIG) welding. The modulation HF pulse reduces the reignition voltage of negative half-wave arc. However, its effectiveness on increasing weld penetration is not evident until the penetration rate (penetration-to-workpiece thickness ratio) exceeds 45%. Above this value, the weld penetration increases significantly with increasing peak current of the HF pulse, and first increased and then decreased with increasing pulse frequency from 10 to 40 kHz. Maximum penetration achieved at optimal welding condition increases by 120% compared with that of conventional AC TIG welding. The grain size and width of partially melted zone are visibly reduced. The average equiaxed grain size, pore number density, and average pore size in HFPM AC TIG weld metal decrease with increasing pulse frequency.