Effect of welding current on morphology and microstructure of Al alloy T-joint in double-pulsed MIG welding

The effect of current on the morphology of Al alloy T-joint in double-pulsed metal inert gas (DP-MIG) welding process was investigated by simulation and experiment. A three-dimensional finite element model and the DP-MIG heat source of double-ellipsoidal volumetric model were developed to simulate the temperature and stress fields under different welding conditions. The macro-morphology and microstructure of welding joints at the corresponding currents were observed in the experiment. The results show that the best condition is at an average current of 90 A and current difference of 40 A, when the maximum temperature is 200 °C higher than the fusion points, with the temperature difference of about 100 °C and stress change of 10 MPa between thermal pulse and thermal base. Under these conditions, Al alloy T-joint with proper fusion condition has smooth fish-scale welding appearance and finer microstructure. Furthermore, the thermal curves and stress distribution in the experiment are consistent with those in the simulation, verifying the precision of the welding simulation.