Ab initio study of planar defects in Ni and Co base superalloys
Aparna P.A. Subramanyam, ICAMS, Ruhr University Bochum, Bochum, GermanyThomas Hammerschmidt, ICAMS, Ruhr University Bochum, Bochum, GermanyRalf Drautz, ICAMS, Ruhr University Bochum, Bochum, Germany
The high temperature strength of superalloys is due to the deformation resistant precipitates of L12 type. One of the plastic deformation mechanisms is through dislocation shearing of these precipitates by the formation of planar defects. Knowledge of the formation energy of planar defects and its modification by alloying elements is therefore a central prerequisite to understanding plastic deformation in superalloys. In this study, we investigate the structural stability of superlattice intrinsic and extrinsic stacking faults (SISF and SESF), anti-phase boundaries (APB) in the (111) plane, complex stacking faults and twin boundaries in the L12 phase of Ni3Al, Co3Ti, (Ni;Co)3Al, Co3(Al;W) and Co3(Ti;Cr) using density functional theory calculations. For Ni3Al, (Ni;Co)3Al and Co3(Al;W), we discuss segregation effects of transition metals to the APBs and twin boundaries. We also discuss the influence of sublattice disorder on the formation energy of planar faults.