The tensile creep-fracture properties of DZ17G. a directionally solidified superalloy, were inves-tigated at 830~ 900℃. The results show that all of the creep curves exhibit negligible primary creep, relatively little steady-state creep and dominant tertiary creep stage. The higher apparent activation energy for creep (540 kJ/mol ) suggests that the creep is controlled by Orowan bowing process. A large ratio of the fracture time to the onset time of tertiary creep is the consequence of microstructure change, i.e., γ particles oriented coarsening parallel to the applied stress axis.The creep fracture data follow the Monkman-Grant relationship. The transgranuIar fracture mechanism proposed on the basis of the metallographic examinations is the linkage of the creep cracks which initiate at the discontinuities with the microstructure (such as the cast porosity,and the carbide/matrix intedece) and also at the specimen surface, that propagate along the γ/γ intedece with perpendicular to the applied stress axis, and the process of crack propagation can be described by the Tien model.
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