Experimental Investigation and Numerical Study on the Elimination of Porosity in Aluminum Alloy Laser Welding and Laser-GMA Welding

Keyhole-induced porosity can strongly weaken the joint strength during aluminum alloy laser welding. Two factors are proposed to be responsible for the porosity formation: bubble formation caused by the instability of the keyhole and bubble captured by the solidification interface. Based on numerical and experimental results, the porosity is suppressed with preheating, due to the capillary stability of the keyhole and easy escape of bubble. N-2 shielding gas has a minor effect on keyhole stability, but it reduces the porosity number as N-2 bubble can dissolve into the liquid aluminum alloy melt pool quickly. The laser-gas metal arc (laser-GMA) welding process can stabilize the metallic plume and enlarge the weld pool. As a result, few spatters and bubbles are formed, and bubbles are easily escaped, both of which contribute to the suppression of porosity.