Insight into γ-Ni/γ′-Ni₃Al interfacial energy affected by alloying elements

Interfacial energy (σ_γ/γ′) of the γ-Ni/γ′-Ni₃Al interface is critical to understand and design Ni-based superalloys. In the present work, a first-principles methodology with constrained relaxations has been used to study the effect of dilute alloying element (X) on σ_γ/γ′ of the (100) coherent interface, where the sixteen X's include Al, Co, Cr, Fe, Hf, Mo, Nb, Pd, Pt, Re, Ru, Ta, Ti, W, Y, and Zr. σ_γ/γ′ = 19 mJ/m² has been predicted for the unalloyed γ/γ′ interface, agreeing well with the previous estimations. It is found that the σ_γ/γ′ value is the lowest when alloying element is in γ-Ni, while the addition to γ′-Ni₃Al increases σ_γ/γ′ due mainly to the in-plane lattice expansion. Specifically, our calculations show that alloying elements Mo, W, and Re have the largest effect on the σ_γ/γ′ value by decreasing it to 4–5 mJ/m² when partitioned to γ-Ni; Ru and Pt are shown to increase greatly the σ_γ/γ′ value up to 25–28 mJ/m² when partitioned to γ-Ni; all ternary additions substituting for Ni in γ′-Ni₃Al increase σ_γ/γ′ except for Pt; and for Ti and Ta, which segregate strongly to γ′-Ni₃Al and substitute for Al, the σ_γ/γ′ values increase to 32 and 35 mJ/m², respectively.