Numerical study of heat and mass transfer in dissimilar laser welding of Mg/Al lap-joint with Ti interlayer

Ti interlayer provides an effective method for Mg/Al laser welding. However, the underlying mechanism of molten pool flow behavior and metal mass transfer process remains unclear. Therefore, a 3D model of Mg/Al laser welding with Ti interlayer is established to study the influences of laser power and interlayer thickness on the molten pool dynamics and metal mass transfer process. The simulation results reveal that the mechanism of metal mixing is the molten Al flows upward, breaking the Ti interlayer and mixing with Mg to form intermetallic compounds. When Ti layer thickness is fixed, the increase in laser power results in an expansion in the recoil pressure, and more molten Al flows upward to mix with Mg. As the Ti layer thickness is increased from 0.2 mm to 0.4 mm, the ideal power interval improves from 100 W to 200 W. At the ideal power interval, the effect of preventing the molten Al from flowing upward is enhanced, and the maximum upward velocity of molten Al is decreased from 0.45 m/s to 0.19 m/s. When the Ti layer thickness is more than 0.3 mm, the large amounts of Mg-Al IMCs formation are suppressed under the ideal power interval. The investigation of elemental distributions in the molten pool of Mg/Al dissimilar metals with Ti interlayer provides new insights into the inhibition of the IMCs formation, significantly contributing to the design and optimization of welding process parameters.