High-Temperature Tensile Creep Behavior of A [001] Orientation Single Crystal Nickel-Base Superalloy

摘要

By means of the measurement of creep curves and microstructure observation, an investigation has been made into the microstructure evolution of yi phase in [001] orientation single crystal nickel-base superalloy during tensile creep. Results show that, after full heat treatment, the microstructure of the single crystal nickel-base superalloy consists of the cubical yi phase embedded, coherently in the y matrix, and arranged regularly along the (100) orientations. During tensile creep, the cubical yi phase in the alloy is transformed into the rafted structure along the direction vertical to the applied stress axis. During steady state creep, the strain rate of the single crystal nickel-base superalloy is controlled by the climbing of dislocations in the ranges of the applied temperatures and stresses. After crept up to fracture, various morphologies of the rafted yi phase are displayed in different regions of the specimen, and the coarsening and twist extent of the rafted yi phase increase as the distance from the fracture decreases, which is attributed to the increment of the effective stress and strain extent in the necked region.