Effect of alloying elements on the γ’ antiphase boundary energy in Ni-base superalloys

Abstract

Mechanical and fatigue performance of γ-γ′ Ni-base superalloys are strongly affected by the antiphase boundary energy (APBE) of the γ′ precipitates which, in turn, is dictated by the alloy's composition. Due to the multicomponent character of these alloys, establishing composition-APBE relationships are challenging, even though the qualitative effect of individual solutes on the APBE may be known. This work attempts to utilize density functional theory-based cluster expansion calculations to systematically assess the effect of composition on the APBE of the γ′ phases in Ni-base superalloys. We aim to elucidate the influence of not only one single element but also multiple coexisting alloying elements on the γ′ APBE. By explicit consideration of configurational disorder via Monte Carlo sampling, the effect of temperature on the APBE has also been analyzed. This work reveals that (1) effects of individual solute element M on the APBE energy obtained in an isolated, ternary condition (i.e. in Ni3-xAl1-yMx+y) does not directly translate to a multi-solute case and that (2) the mutual synergistic interactions among different solute elements are not negligible. Based on the present results, an empirical master equation that predicts the APBE based on the composition of the γ′ phases has been obtained.