A solidification model for atomization

A microsegregation solidification model has been extended for an individual droplet falling through a stagnant gas during the atomization process. Assuming a uniform temperature within the droplet, the model takes into account nucleation undercooling and equiaxed growth of the dendritic and eutectic microstruc-tures until complete solidification.1 It predicts the temperature evolution and the chemical segregation within the droplet in terms of the percent of the dendritic and eutectic microstructures. Extensive experiments have been performed on Al-Cu droplets using the impulse atomization technique. The distribution of phases, cell spacing and segregation have been quantified earlier.2-4 It has been reported that the amount of eutectic in the droplets falls below the equilibrium prediction as the alloy composition increases. Successful comparison between the model results and the experiments leads to the conclusion that eutectic undercooling and eutectic recalescence play a very important role in the final percent of eutectic in the droplets. © 2009 ISIJ