Modeling of the solidification of gas-atomized alloy droplets during spray forming

In order to describe the microstructure evolution of a supercooled droplet under the situation that the nucleation and the growth of the grains occur concurrently during spray forming, a model has been developed based on the population dynamics method. This model is solved numerically to investigate the solidification behaviors of the gas atomized Al–4.5 wt.% Cu droplets. The results show that the nucleation takes place under a critical supercooling for a given droplet. The grain sizes are significantly different during the period of nucleation and recalescence, but become uniform with the progress of the solidification. In addition, a smaller droplet has a higher cooling rate and a finer microstructure at the end of the solidification.