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

Abstract

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.

Stochastic modeling of columnar dendritic grain growth in weld pool of Al‐Cu alloy

“…The advantage of the CA-FD model is that the macroscopic temperature field analysis and the microstructure simulation can be performed simultaneously. The CA-FD model applied in the current study has been described elsewhere [21] and will not be repeated in detail here.…”

“…The welding speed is 3.5 mm/s and the welding current and voltage is 120 A and 12 V (AC) respectively. Based on these parameters, the temperature field is solved firstly by the finite difference method based on the heat transfer and conservation theory in the weld pool [21]. The specimen is fixed and the heat source moves along the surface of the sample.…”

“…Simulating the mesostructure and microstructure of HAZ (heat-affected zone) are studied too for several years [17][18][19]. And even the grain growth during solidification process of weld pool is simulated [1,[20][21]. However, there are many fields expected to be improved because the grain growth in the weld pool is very complicated, especially in the transition from the cellular to columnar dendritic grain and the branching mechanism and the growth of secondary dendrite arms in the weld pool is very different from the one in casting condition.…”

Columnar grain growth pattern with fluid flowing in molten pool

“…However, only a few of these researches refer to welding process [5][6][7][8]. Among those researches, fluid flow behavior is seldom taken into account.…”

3D Coupled Cellular Automaton (CA)–Finite Element (FE) Modeling for Solidification Grain Structures in Gas Tungsten Arc Welding (GTAW)

“…The temperature gradient and the solidification velocity in the weld pool were provided by a solution of the heat flow using the Finite Difference Method (FDM). Zhan et al 13,14) developed the morphological evolution of columnar dendrites in the weld pool. The constitutional and curvature undercooling were considered in the computation of the solid-liquid interface velocity and provided by the FDM.…”