Effects of Elevated Withdrawal Rate on the Microstructure and Segregation Behavior of a Nickel-base Single Crystal Superalloy

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 rates. Also, the size of γ/γ' eutectic becomes small while the total volume fraction increases. Considering the composition segregation is determined by diffusion time of the constituent elements, when withdrawal rate is elevated, diffusion time of solutes decreases, and the effects of segregation are enhanced.