Coupling Effect of Ni and Ta on the Antiphase Boundary Energy in Γ’ Phase of Coni-Based Superalloys

Abstract

Anti-phase boundary (APB) significantly affects the yield strength and creep behavior of CoNi-based superalloys. Given the conflicting evidence regarding the effect of Ni on the APB energy (APBE) of the γ’ phase, we have conducted a comprehensive investigation using a combination of density functional theory, cluster expansion, and Monte Carlo simulation techniques. Our analysis of equilibrated configurations reveals that Ni plays a crucial role in preventing the formation of anti-site defects, thus enhancing the stability of the γ’ phase. Additionally, we identified short-range order phenomena within the γ’ phase, which further contribute to phase stability. Regarding the APBE, both Ni and Ta increase the APBE within a reasonable composition range. Moreover, the simultaneous addition of Ni and Ta further increases the APBE, demonstrating a synergistic effect. However, increasing the Ni concentration in certain CoNi-based superalloys leads to a reduction in Ta content, which in turn lowers the APBE. Our findings provide a clear understanding of the roles of Ni and Ta in determining the APBE and offer a foundation for manipulating the shear mechanism in γ’ phases.

Keywords: CoNi-based superalloys, Density functional theory, cluster expansion, γ' phase stability, anti-phase boundary energy, short range order