(A) study on the chemical and mechanical properties of the topologically close-packed phase in Ni-based superalloys

Abstract

In the development of superalloys, the formation of topologically close-packed (TCP) phase is a significant concern as it can negatively affect the microstructural stability and mechanical properties of single-crystal Ni-based superalloys. In order to suppress the formation of TCP phase, the Ru-containing alloys and Re-free alloys have been developed during past three decades. However, the effect of Ru addition on the TCP phase formation is still controversial, and there is a lack of understanding in the role of TCP phases on the deformation behavior. To address these issues, in this dissertation, the influence of Ru addition on the precipitation behavior of TCP phases and its underlying mechanism were investigated through atomic-scale characterizations, including atom probe tomography (APT) and transmission electron microscopy (TEM). Additionally, the role of TCP phases on the mechanical property degradation and the TCP-related deformation mechanism were examined through multi-scale mechanical testing.