Recent progress in developing CoNi-based superalloys has achieved improved properties [1] and 3D printability [2]. These alloys are primarily strengthened by γʹ (L1₂ structure) precipitates. The effect of alloying on the precipitate strength is well documented for Ni₃(Al,X) (X=Ti, Ta, W, Nb, Mo, V etc) [3], (Ni,Co)₃Al [4] and Co₃(Al,W) [5] compositions. Beyond these ternary compositions, however, the synergistic effects of alloying on the mechanical properties of L1₂ precipitates are not understood. Here, we present a simple yet elegant framework for understanding these synergistic effects in quaternary and quinary spaces. Since planar fault energies are effective descriptors for the shear resistance of these precipitates [6], we systematically calculate the anti-phase boundary (APB) energies and capture the synergistic effects on APB energies in (Co,Ni)₃(Al,W,Ta).

Employing the novel diffuse multi-layer fault (DMLF) model, structural energies in the proximate γ'_a and L1₂ structures are evaluated using density functional theory calculations for specific compositions in (Co,Ni)₃(Al,W,Ta). The APB energies were estimated from these structural energy differences. Domains with stable L1₂ regions are identified using ThermoCalc predictions. Within the stable L1₂ regions, our preliminary results suggest that APB energies in CoNi-base alloys are smaller than in Ni-base and Co-base compositions. To validate the theoretical predictions, a series of different alloy compositions with varying APB energies were selected. These compositions were melted, homogenized, and subsequently characterized for mechanical properties and microstructure post-deformation. The design methodology, simulation results, validation with experimental results will be presented in detail at the conference.