Research on formation and stability of keyhole in stationary laser welding on aluminum MMCs reinforced with particles

Abstract

The formation and stability of keyhole in stationary laser welding on aluminum metal matrix composites reinforced with particles are studied using a numerical simulation. The interaction between molten pool and reinforcement particles is evaluated by using the particle–fluid coupling model in the numerical simulation. In order to study the effect of different volume fractions of particles on the keyhole stability and fluid flow inside the molten pool, keyhole formation process, variation of free surface, temperature distribution, and fluid flow are calculated numerically, respectively. The calculation results show that the keyhole is stable at the beginning under different conditions and then the protrusion occurs inside the keyhole with increasing calculation time. The flow behavior of molten pool affected by particles and forces acting on the surface could explain the forming of humps inside the keyhole, which directly cause the variation of the keyhole. As the volume fraction of TiB₂ particles increases, the keyhole is more likely to be instable and the oscillation occurs at an earlier time. Fluctuations of the surface tension and recoil pressure due to the uneven distribution play an important role in the instability of the keyhole.