Phase field modeling of dendritic coarsening during isothermal solidification

Dendritic coarsening in Al-2mol％Si alloy during isothermal solidification at 880K was investigated by phase field modeling.Three coarsening mechanisms operate in the alloy:(a) melting of small dendrite arms; (b) coalescence of dendrites near the tips leading to the entrapment of liquid droplets; (c) smoothing of dendrites.Dendrite melting is found to be dominant in the stage of dendritic growth,whereas coalescence of dendrites and smoothing of dendrites are dominant during isothermal holding.The simulated results provide a better understanding of dendrite coarsening during isothermal solidification.