This study addressed the gas metal arc welding (GMAW) of Al 5183 aluminum alloy using variable polarity (VP). The effects of the electrode negative (EN) pulsing ratio and repetition frequency on the geometrical features and microstructural evolution of the deposited materials were investigated and discussed. The current and voltage were manually controlled independently for each phase to evaluate the effect of the polarity change. The influence of phase and its changing frequency on the geometrical features and microstructure evolution were observed. The phase of the electrode affected the arc concentration and changed the amount of the deposited material and the dilution between the substrate. The EN phase is beneficial for making a finer structure than the electrode positive (EP) phase because of the lower heat input per unit mass. In addition, the size of the grains decreased as the phase change frequency increased. When the number of repetitions frequency increased within a cycle, the size of the microstructure was reduced. Consequently, strategies can be established to minimize the microstructure with VP-GMAW welding using a high EN pulsing ratio and low repetition conditions.

Due to the high thermal diffusivity and metallurgical sensitivity, the proper welding processes of the aluminum are required. The Laser beam welding and friction stir welding processes have been focused as the appropriated welding processes for aluminum. The heat treated 6xxx series and 7xxx series aluminum sheet were welded by the laser beam welding and friction stir welding processes. Also, the effects of heat input through the welding parameters were investigated. The tensile strength of weldments was evaluated respectively and compared by the processes and heat input level. The insignificant tensile strength differences were found for the 6xxx series by the welding processes. However, the friction stir welded 7xxx series weldments were shown 82~89% joint efficiency while laser beam welded weldment were shown 48~58%. Overall, the effect of heat input level was not revealed in this experiment range. The degradations in hardness of weldments tended to be in proportion to the joint efficiency loss.