Ni Al W

1. On the interplay between W and Ta atoms in Ni-based superalloysDavid N. Seidman , Northwestern University,DMR 0804610 Ni-based superalloys are used for turbine blades in aeronautical jet engines and power generators. They derive their properties for high-temperature applications from their two-phase g(fcc)/g’(Ni3Al) microstructure, and the partitioning of refractory elements to the g- and g’-phases determines their mechanical properties at elevated temperatures. We investigated the partitioning behavior of W in a multi-component Ni-based superalloy and in a ternary Ni-Al-W alloy using atom-probe tomography (APT) and first-principles calculations. APT observations indicate that whereas W partitions preferentially to the g’-phase in the ternary alloy, its partitioning behavior is reversed in favor of the g-phase in the multicomponent alloy, which is explained using first-principles calculations. g g g’ g’ Ni Al W A 3D-APT reconstruction showing the partitioning of W (large spheres) to the g- phase in (a) themulti-component alloy, and to the g’- phase in the (b) ternary alloy: also shown, Ni (green) and Al (red). Y. Amouyal, Z. Mao, C. Booth-Morrison, and D. N. Seidman, Appl. Phys. Lett. 94 (4), 041917 (2009)

2. On the interplay between W and Ta atoms in Ni-based superalloysDavid N. Seidman , Northwestern University,DMR 0804610 We performed first-principles calculations of the substitutional formation energies of W and Ta at different locations on both sides of the g/g’ interface (above), indicating that Ta has a larger driving force for partitioning to the g’-phase than does W. We conclude that Ta displaces W from the g’- into the g-phase in multi-component alloys. Y. Amouyal, Z. Mao, C. Booth-Morrison, and D. N. Seidman, Appl. Phys. Let. 94 (4), 041917 (2009)