|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Gamma (FCC)/Gamma-Prime (L12) Co-Based Superalloys II
||Structural Stability of L12 and TCP Phases in Co-based Superalloys
||Thomas Hammerschmidt, Arthur F. Bialon, Jörg Koßmann, Ralf Drautz
|On-Site Speaker (Planned)
The further development of Co-based superalloys requires to optimise the γ/γ' microstructure and to suppress the precipitation of topologically close-packed (TCP) phases. Both optimisation targets depend directly on the local chemical composition. In order to gain an understanding of the formation of L1<SUB>2</SUB> and TCP phases, we apply structure maps that relate the structural stability of a compound to its chemical composition. The alloying elements enter in terms of the number of valence electrons, the atomic volume and the electro-negativity. By combination with casting experiments and microstructure analysis, we demonstrate that a structure map for intermetallic phases correctly predicts TCP-phase precipitates from experimentally determined local chemical compositions in Co-based superalloys. From the stability window of the L1<SUB>2</SUB> phase in a structure map for sp-d valent compounds we can determine modifications of the chemical composition of Co<SUB>3</SUB>(Al,W) that are likely to form a γ/γ' microstructure.