Microstructure and mechanical properties of pulse MIG aluminum alloy welded joints by means of a novel multi-strands composite welding wire

In this study, a novel multi-strand composite welding wire was adopted in 5A06 aluminum pulse MIG welding method, and the microstructures and properties of aluminum alloy multi-strand composite wire welded joints were compared with those of traditional TIG welded joint. The results show that the welded joint used by this novel wire has a better tensile strength, which reaches up to 340 MPa (86.7% of the base metal). The performance of MIG welded joint is similar to that of TIG welded joint, and it can improve welding efficiency by about 4 times. It is also found that the softening of the heat affected zone of the welded joint is mainly affected by the larger grain size and the higher recrystallization ratio, the lower Mg content as well as the coarsening and reduction of the precipitated phase caused by higher heat input. In addition, the pulse MIG welding method with this novel wire can reduce the heat input in welding process, refine grains, and can significantly weaken the loss of Mg element and precipitation. Based on these advantages, the softening of the pulse MIG welded joint decreases and the excellent properties of welded joint can be obtained.