Effect of Solidification Interface Morphologies on Microstructures of a Ni-base Superalloy
摘要
A cast Ni-base superalloy K5 was directionally solidified and various solidification in- terfaces including plane front,cellular, cellular-dendritic and dendritic were obtained in a wider range of G/R ratio by using improved high withdrawal device and liquid metal cooling experi- mental sets.The precipitation pattern of some prin- cipal phases of the alloy and correlation of the vari- ous interfaces with microstructure were studied sys- tematically.It was indicated that the morphology of solidification interface of superalloy K5 varied with G/R ratio and that the solidification interface morphologies have a considerable effect on the fea- tures of phases both precipitated during solidification and post-solidification.Plane front and cellular directional solidification of superalloy K5 lead to a substantial decrease of MC carbide and elimination of γ-γ'eutectic,but make needle-shape M_6C carbide precipitate easily during ageing treatment.The finer dendritic structures solidified under the condition of higher cooling rate have less dendritic segregation and ideal microstructure.