Modelling of Secondary Dendrite Arms Evolution during Solidification by a Phase-field Method

Mechanical property of cast metals is strongly dependent on solidification structure, in particular the secondary dendrite arms spacing. In this study a Phase Field Method was used to simulate the evolution of dendritic structure with coupled heat and solute diffusion during solidification. Coarsening and remelting of the secondary arms were simulated. It is found that (1) the base of the secondary arms doesn't decrease as coarsening theory predicts and the arms spacing keeps unchanged when the arm grows into a steady state, but the volume of the arms increases; (2) both remelting of secondary arms and coarsening of secondary arms can be observed, which agrees with the coarsening theory and experiment observations.