Multi-scale Simulation for the Columnar to Equiaxed Transition in the Weld Pool

Abstract

The heat and mass transfer behavior and the morphological evolution of the solidification structures in the weld pool were simulated by the multi-scale model which combines the finite element (FE) and the cellular automata (CA) methods to investigate the columnar to equiaxed transition (CET) process during welding. The grain structure evolution within the entire weld and the competitive dendrite growth at different locations were studied to better understand the CET process. The results indicate that with the decrease of the distance to weld center, the undercooled zone width and the maximum undercooling increase. In this case, more equiaxed dendrites form in the undercooled melt, and the distance between the equiaxed dendrites and the columnar front also becomes lager. There is more space for the equiaxed dendrites to grow up and block the columnar dendrites. Therefore, the equiaxed dendrites become more competitive, and the CET tendency increases.