Porosity suppressing and grain refining of narrow-gap rotating laser-MIG hybrid welding of 5A06 aluminum alloy

The rotating laser was used in the narrow-gap rotating laser-MIG hybrid welding (NG-RLMHW) of 5A06 aluminum alloy to suppress porosity and improve joint performance. The results show that a suitable rotating laser can effectively reduce the porosity and improve the quality of 5A06 aluminum alloy NG-RLMHW joints. When rotation frequency f=25 Hz and rotation diameter d=3 mm, the porosity RP is 1.12% and the average ultimate tensile strength Rm is 314 MPa. The sidewall fusion of NG-RLMHW joints is also improved by the rotating laser. Due to the significant stirring effect of rotating laser on the molten pool, the minimum grain size of 5A06 aluminum alloy NG-RLMHW joints is about 28% lower than that of joints welded without rotating laser. Meanwhile, because the energy distribution in the molten pool of NG-RLMHW is more uniform, the temperature gradient G of molten pool is reduced and the morphology transformation from columnar grain to equiaxed grain in the weld metal is promoted.