Macrosegregation forms during phase separation period and phase separation time increases with the increase of melt undercooling (a). It always takes place regardless of undercooling on the Earth's ground. The phase with larger density, such as Cu-rich phase settles down to the bottom (b) due to Stokes motion. The Stokes motion velocity increases with the increase of droplet radius (c). The solute contents in Co-rich zone decrease with the enhancement of melt undercooling (d) and (e).