Effect of the laser power on the microstructure and mechanical properties of the laser-MIG hybrid welding joints of the 2195 Al–Li alloy

In the present study, 2195 aluminium–lithium (Al–Li) alloy joints were welded by laser-metal inert gas (laser-MIG) hybrid welding. The effect of different laser powers (700, 1000, and 1300 W) on the microstructures and mechanical properties of the weld joints was investigated. The dendritic solidification structure of the weld joint comprised the α-Al, θ-(Al2Cu), and T-(AlLiSi) phases. When the laser power increased, the grains coarsened, and the amount of the precipitated phase decreased. Consequently, the micro-hardness of the weld decreased. The heat input also increased with the increase in laser power. This increased the fluidity and solidification time of the liquid metal at the bottom of the molten pool. Therefore, the deposition of the particles of the refractory metal compounds and the formation of the equiaxed grain zone (EQZ) was hindered.