|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Gamma (FCC)/Gamma-Prime (L12) Co-Based Superalloys II
||Double Minimum Creep of a Ta-containing Single Crystal Co-base Superalloy
||Fei Xue, Christopher Zenk, Steffen Neumeier, Mathias Göken
|On-Site Speaker (Planned)
Tantalum is one of the most effective alloying elements to improve the mechanical properties of γ′-hardened Co-base superalloys. To further study how Ta affects the lattice misfit and creep behavior, high temperature neutron diffraction experiments and creep tests at 950°C were performed on a single crystalline Co-Al-W-Ta alloy. The diffraction experiments show that a positive misfit with large magnitude exists even at 950°C, leading to pronounced rafting during creep. The creep curves feature two creep rate minima and interrupted creep tests at different strains were conducted to study the microstructural evolution and deformation mechanisms. It is shown that rafting starts before the first creep minimum, dislocations cut the rafts and elements segregate to the stacking faults with ongoing creep deformation. The creep performance of several Co-Al-W-Ta alloys with different chemical compositions from the γ-γ′ tie line was additionally investigated to understand the connection between γ′ volume fraction and creep behavior.