Laser pressure welding of Al-Li alloy 2198: effect of welding parameters on fusion zone characteristics associated with mechanical properties

Al-Li alloy 2198 exhibits good combination of toughness and strength but its application is strongly limited by the poor weldability due to the formation of porosities during fusion-welding. This is the first study proposing and verifying a new approach to produce defect-free laser welds of poorly fusion-weldable Al-Li alloy 2198 with applied external pressure, i.e., feasibility of laser pressure welding to Al-Li alloy 2198 was examined. The microstructures associated with tensile shear behavior of laser pressure welded Al-Li alloy 2198 obtained at various welding parameters were analyzed. The results showed that formation of the welding defect in the weld could be successfully suppressed by applying laser pressure welding, even without shielding gas. Three microstructural zones, including the chill zone, the columnar zone and the equiaxed zone were observed in the fusion zone. Size of fusion zone and area fraction of porosities generally increased with increasing roller pressure and welding heat-input, and they dominantly affected the tensile shear behavior, including the peak load and the failure mode, of the weld.