The evolution of polycrystalline solidification in the entire weld: A phase-field investigation

The solidification patterns are dominated by the surface tension of solid/liquid interface and the transfer process of heat and mass. The continuously changing solidification parameters in the molten pool make the differences between welding and directional solidification. It could enhance our understanding of solidification behavior to investigate the solidification evolution in the molten pool, with dynamic and nonlinear temperature field. In this paper, the evolution of polycrystalline solidification in the entire weld was performed. Specifically, the welding thermal process was simulated through the finite element method, and the solidification process was simulated by the phase-field model. The comparison between the simulation and experimental result shows good agreement in general, which validates the accuracy of current model. Based on the simulation results, the dynamical solidification evolution during welding was discussed, including planar instability, epitaxial growth and competitive growth. Then the effects of surface tension and grain size on solidification were investigated. The simulation results demonstrate the ability and accuracy of phase-field model reproducing the evolution of polycrystalline solidification in the entire weld. The investigations in this paper lay the foundation for clearly revealing solidification behavior in the molten pool. (C) 2019 Elsevier Ltd. All rights reserved.