|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Gamma (FCC)/Gamma-Prime (L12) Co-Based Superalloys II
||Superlattice Intrinsic Stacking Fault Energies and Solute Segregation to Planar Defects in Co-based Superalloys
||Michael S Titus, Robert K Rhein, Alessandro Mottura, Min-Hua Chen, Anton Van der Ven, Tresa M Pollock
|On-Site Speaker (Planned)
||Michael S Titus
Co-based superalloys strengthened by the γ’-(L12) phase exhibit comparable and, in some cases, superior high temperature creep resistance to 1st-generation Ni-based superalloys. Despite the comparable creep resistance between Co- and Ni-based superalloys, the high temperature creep deformation modes are markedly different: the γ’ phase in Ni-based superalloys is typically sheared via coupled a/2<110> matrix dislocations, whereas the γ’ phase in Co-based superalloys is sheared via Shockley superpartial a/3<112> dislocations, which leave superlattice intrinsic stacking faults (SISF) behind in their wake. We have calculated the SISF energies over a broad range of compositions via density functional theory (DFT), including both Co3(Al,W)- and Co3(Al,Mo)- based alloys. Incorporating vibrational free energy, we have calculated the temperature-dependent SISF energies. The SISF energies will be linked to the observed solute segregation behavior at SISFs, and implications for improving high temperature Co-based superalloy strength will be discussed.