Cu segregation of two varieties of Al-Si-Cu alloy w it h different solidification behaviors under partial pressurization conditions was researched. It was found that Cu segregation of the AC4B alloy with mushy solid i fication was susceptible to negative segregation located below pressurrization b ar and dependant on the time of initial pressurization

while the ADC12 alloy wi th unidirectional solidification only exhibited slightly negative segregation in annular position about 5 mm below pin tip and was not dependant on the time of initial pressurization. In contrast

it presented positive segregation. The Cu segregati on was attributed to the local flow of the condensated liquid through interdendr ite.