On the interplay between tungsten and tantalum atoms in Ni-based superalloys: An atom-probe tomographic and first-principles study

The partitioning behavior of W in a multicomponent Ni-based superalloy and in a ternary Ni-Al-W alloy is investigated using atom-probe tomography (APT) and first-principles calculations. APT observations indicate that whereas W partitions preferentially to the γ′ (L 12) -precipitates in the ternary alloy, its partitioning behavior is reversed in favor of the γ (fcc) -matrix in the multicomponent alloy. First-principles calculations of the substitutional formation energies of W and Ta predict that Ta has a larger driving force for partitioning to the γ′ phase than W. This implies that Ta displaces W from the γ′ -precipitates into the γ -matrix in multicomponent alloys.