An ab initio method based upon density functional theory was used to compute the zero-temperature antiphase boundary energies for Ni3Al1-xRx (R = Nb, Ta, Ti) over a range of compositions. The calculations were limited to an antiphase boundary on the (111) plane of the L12 crystal structure; allowing only the volume relaxation which was appropriate for a γ′ precipitate in Ni-based superalloys. For the limiting case of the binary system, Ni3Al, the antiphase boundary energy was also calculated for the (100) plane. It was found that the antiphase boundary energy for the (111) plane in Ni3Al was 181mJ/m2. Substitution of Nb, Ta or Ti at the Al site increased the antiphase boundary energy to over 600mJ/m2, leading to higher strengths. While the peak antiphase boundary energy values for all of the ternary systems were quite similar, they were achieved over very different compositional ranges. The Nb and Ta were found to have almost identical strengthening effects on Ni3Al.

First-Principle Calculation of APB Energy in Ni-Based Binary and Ternary Alloys. M.Chandran, S.K.Sondhi: Modelling and Simulation in Materials Science and Engineering, 2011, 19[2], 025008