The cooling process of the Al-Si alloy were analyzed by a model

in which the heat transfer equation of atomized alloy droplets coupling with motion equation was considered

to understand effects of droplet size

initial gas velocity

super-heat of the melt on cooling process and microstructure of the A390 alloy.It is found that

with decreasing in size of droplet

the obtained cooling rate and under-cooled rate are raised.When the droplet size is decreased to below a critical size

temperature change and microstructure of the droplets are sharply transformed.Precipitation of primary phase can be restrained by increasing initial velocity of atomized gas and decreasing superheating rate of melt

which is beneficial to the refinement of microstructure of Al-Si alloy.