Molten pool dynamics in laser shock modulated laser melting process: evolutionary processes and mechanism analysis

Laser additive manufacturing (LAM) has emerged as a transformative solution with broad industrial applications. But non-optimal processing parameters may induce defects including coarse grains, porosity, and cracks. Auxiliary energy fields modulation, particularly pulsed laser modulation, offers a novel strategy for LAM process control, distinguished by its equipment simplicity and non-contact advantages. However, there is a lack of systematic simulation studies on its transient heat transfer, flow behavior as well as solidification. In this study, the dynamic evolution of laser shock modulated molten pool processing (LSMMP) is investigated experimentally and through simulations based on Ti6Al4V. Numerical simulations show that the application of the pulsed laser can significantly change the convection state in the molten pool and produce characteristic surface ripples on the molten track. At 600 mJ/900 mJ single pulse energies, peak velocity increased by approximately 25%/300% respectively, solidification front temperature gradient (G) decreased approximately 21%/48% , and cooling rate (G×R) decreased approximately 21%/46%. Meanwhile, the G/R values decreased significantly. The experimental results show that the morphology of the characteristic surface ripples is similar to the simulation results, and LSMMP can inhibit the generation of columnar crystals.