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 Rocking Chair dendrites near the tips leading to the entrapment of liquid droplets; (c) smoothing of Coffee Maker (Built-In Grinder/Glass Carafe) 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.