Stability of high energy superlattice faults in Ni-based superalloys from atomistic simulations

Abstract

High energy stacking faults generated by lattice dislocations entering the strengthening precipitates of Ni-based superalloys are responsible for the unique mechanical properties of these structural materials. However, the question about stability of these faults has not received the attention it deserves. Using atomistic simulations, we show that the anti-phase boundary (APB) can spontaneously transform into super intrinsic stacking fault (SISF) and the complex stacking fault (CSF) can spontaneously transform into L1₂ lattice structure. The former transformation explains the experimentally observed presence of isolated SISFs and super extrinsic stacking faults (SESFs) in the precipitates. Finally, multiple studies were focused on finding alloying additions which increase the APB and CSF energies. We demonstrate therefore that alloying additions which increase stacking fault energies may conversely decrease their stabilities.