EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

High strength Ni-based superalloys are of great importance for high-temperature industrial applications due to the existence of the ordered L12 Ni$_3$Al phase (γ’ precipitates). The antiphase boundary energy (APBE) associated with the γ’ precipitates determines the mechanical properties when dislocations cut through the precipitates. In this work, the temperature-dependent APBEs of the L12 Ni$_3$Al phase along (100) and (111) planes are investigated based on ab initio density-functional-theory (DFT) simulations including all relevant thermal excitations. Especially, the explicit anharmonic free energy is efficiently and accurately computed within the framework of thermodynamic integration by the recently developed moment-tensor-based machine-learning potentials fitted with ab initio molecular simulation data. Our results show that local magnetic states have a strong impact on the APBE. Particularly when electronic excitations are also considered at finite temperatures, the magnon-electron coupling effect results in non-magnetic states above a critical temperature and thus lower the APBE compared to the ferromagnetic calculations. Our predicted APB free energies are also compared with available experimental data.