Numerical analysis of molten pool-particle behavior in wire-fed laser welding of 7075 aluminum alloy with TiC reinforced filler wire

A high-fidelity computational fluid dynamics-discrete phase model (CFD-DPM) coupled model was developed to investigate the heat transfer, fluid flow, and TiC particle migration behavior during wire-fed laser welding of 7075 aluminum alloy with 1.2 wt% TiC-reinforced filler wire. The model was validated by comparing the simulated weld bead morphology with experimental results, showing good agreement. The results reveal that the molten pool flow evolves from a dual-vortex structure driven by intense Marangoni convection and droplet impingement in the initial stage to a single-vortex structure in the quasi-steady stage, with the peak flow velocity decreasing from > 0.45 m/s to ∼ 0.25 m/s. This flow transition dominates the spatial redistribution of TiC particles, leading to a heterogeneous distribution characterized by ring-like enrichment near the fusion boundary and depletion in the central weld region. Force analysis indicates that the particle motion is primarily governed by the competition between hydrodynamic drag force and net gravitational force. Particles in different weld regions undergo distinct three-stage migration processes, specifically rapid sinking–rapid ascent–fluctuating suspension in the top region, rapid sinking–modest ascent–quasi-equilibrium suspension in the middle region, and rapid sinking–slow ascent–re-sinking in the bottom region. This work provides fundamental insights into the molten pool-particle interaction mechanism and theoretical guidance for optimizing the laser welding process of particle-reinforced high-strength aluminum alloys.