Study on Fusion Zone Size, Pore Characteristics, and Mechanical Properties of 6063 Aluminum Alloy Cold Metal Transfer Mix plus Synchropulse Welded Joint

ER5183 filler wire is used as filler metal for CMT MIX + Synchropulse welding of 6063 aluminum alloy sheets. The relationships among the fusion zone (FZ) size, pore characteristics, microstructure and mechanical properties are studied. The results show that the heat and convection intensity of the molten pool increase as the heat input increases, so that more base metal is melted and the weld width increases. The porosity and chain-like pores are closely related to the FZ size. The FZ size characteristic index (k) is established to predict the porosity and chain-like pores. The lower the k value is, the more difficult chain-like pores are to generate. Properly increasing the heat input eliminates the chain-like pores without aggravating the softening. The chain-like pores enormously reduce the effective load-bearing area of the FZ, which leads to the pretty poor mechanical properties of the FZ. Considering that the high porosity weakens the fatigue life, it is recommended to properly increase the heat input to improve the service performance of aluminum alloy welded joints on the premise that the full penetration welded joint has been obtained.