Phase-field investigation of dendrite growth in the molten pool with the deflection of solid/liquid interface

The solidification process in the molten pool significantly determines the microstructures of weld metal. The motion of heat source makes the solidification parameters, temperature gradient G and growth rate R, changing continuously across the pool, as well as the solidification modes. It is meaningful to investigate the solidification evolution in the molten pool, with dynamic solidification parameters. The previous researches ignored the deflection of solid/liquid (S/L) interface with time, regarding the normal direction of interface being constant all the time. In this paper, we modified the macroscopic model for G and R without S/L interface deflection to the model with the interface deflection. The solidification parameters were calculated out through the two models and compared with each other. Then the phase-field simulations of dendrite growth in the molten pool were carried out, including single crystal and bi-crystals. The dendrite growth of single crystal and bi-crystals, with the diverging and converging directions, were compared and discussed. The simulations demonstrate that the model considering the interface deflection could represent the dendrite growth during welding more realistically. The investigations lay the foundation for revealing solidification behavior in the molten pool more precisely.