Abstract:The effects of withdrawal rate on the microstructure and segregation behavior of a nickel-base single crystal superalloy were investigated. The results indicate that, by increasing the withdrawal rate, the primary dendrite arm spacing (λ1), the secondary dendrite arm spacing (λ2) and the size of γ" precipitates decrease gradually. Moreover, the shape of γ" precipitates is more regular at higher withdraw velocities. Also, the size of γ/γ" eutectic are smaller while the total volume fraction increased. Considering the composition segregation is determined by diffusion time of the constituent elements, when withdrawal rate was elevated, diffusion time of solutes decreased, the effects of segregation were raised.