Dendritic grain growth simulation in weld molten pool based on CA-FD model

The finite difference model is coupled with a cellular automaton (CA) model to simulate dendrite growth in TIG (tungsten inert-gas) weld molten pool of nickel-based alloys. Based on the macro finite difference computation of the thermal field of the whole weldment, the micro CA model is used to simulate grain formation process in 2-dimension area within weld molten pool. The results illustrate that the complicated thermal field and solute field can lead to complex grain morphologies in weld molten pool. The primary dendrite spacing changes during welding solidification process and the final primary dendrite spacing is decided by the thermal field, solute field and other parameters. And it is indicated that the grain boundary segregation has important relationship with welding speed. The grain boundary segregations become more severe as the welding speed increases when the other parameters are kept unchanged.