Quantitative analysis of synergic effects during laser-arc hybrid welding of AZ31 magnesium alloy

The easy cracked droplet of the magnesium (Mg) arc was stabilized by the synergic effects in laser-arc hybrid welding, but few reports have attempted to quantify their degree, and then use it to explore the stabilization mechanism. According to the relationship between the process stability and real-time arc current, a new dimensionless parameter, i.e., arc current increment (ψ), was proposed to quantitatively characterize the synergic effects by counting the difference in the average arc current between the hybrid welding and metal inert gas welding. The bigger the ψ, the stronger the synergic effects, and the more stable the hybrid process. The ψ increased from 2.7 to 22.7% when the laser power increased from 1 to 4 kW, whereas it decreased from 32.5 to 5.7% when the arc current increased from 90 to 210 A. The quantitative results were well corresponding to the observed phenomena caused by the synergic effects, which were characterized by the plasma shapes and weld surface morphologies. Besides, the stabilization mechanisms of both the burning and droplet transfer of the Mg arc were discussed in terms of the calculated ψ.