Microstructure Evolution and Creep Behaviors of a [111] Oriented Single Crystal Nickel-Based Superalloy

Abstract

By means of microstructure observation and creep properties measurement, microstructure evolution and creep behaviors of a [111] oriented single crystal nickel-based superalloy at 1040 °C are investigated. Results show that, after fully heat treated, microstructure of the alloy consists of the cuboidal γ′ phase embedded coherently in the γ matrix, and arranged regularly along the <100> orientation. After crept for 50 h, the γ′ phase in alloy has been transformed into the mesh-like rafted structure on (010) plane along [001] and [100] orientations. After crept up to fracture, the rafting orientation of γ′ phase is at about 40–60° angle relative to the stress axis. The deformation mechanism of alloy during steady-state creep is significant amount of dislocations being activated in γ matrix and a few dislocations shearing into the rafted γ′ phase. In the latter stage of creep, significant amount of dislocations shear into the rafted γ′ phase, and some dislocations concentrate to form the subgrain structure under the effect of thermal activation.