Nanoscale visualization of early /'-phase separationNSF Grant MET DMR-0241928, Northwestern University, David N. Seidman, PI

Aging experiments at 600°C in a model Ni-7.5 Al-8.5 Cr at.% superalloy

g = [111]

100 nm

10 nm

Atom-probe tomography (APT), left, and transmission electron microscopy (TEM) images, above, allow for nanoscale visualization of /’ phase separation.

[110]

APT image of a spheroidal Ni3AlxCr(1-x) ’-precipitate of radius ca. 9 nm. The (110) planes

are clearly defined by Al (red) and Cr atoms (blue).

A high '-precipitate number density (~1024 precipitates m-3) is detected after 4 hours of aging at 600°C with atom-probe tomography (APT) The resulting composition profiles provide further insight into the phase separation behavior.

Early /'-phase separation: sub-nanometer scale analysesNSF Grant MET DMR-0241928, Northwestern University, David N. Seidman, PI

Precipitation in a model Ni-6.5 Al-9.5 Cr at.% superalloy aged at 600°C

Corresponding composition profilesAPT image

Nanostructural temporal evolution in /'-phase separation

NSF Grant MET DMR-0241928, Northwestern University, David N. Seidman, PI

Precipitation in a Ni-8.5 Al-10 Cr-1.0 Ru-1.0 Re at.% model superalloy

Atom-probe tomograph (APT) images of a Ni-8.5 Al-10 Cr-1.0 Ru-1.0 Re at.% model superalloy aged at 600ºC for 15 minutes, acquired on the 3-D LEAP™ tomograph at the Northwestern University Center for Atom-Probe Tomography (NUCAPT). The morphologies of the ’-precipitates are found to be a mixture of spheroidal and interconnected precipitates. - Courtesy of Ms. Gillian Hsieh, an R.E.U. student working with the group.

The Kinetic Pathway for Coarsening in a Ni-Al-Cr alloy by Lattice Kinetic Monte Carlo Simulation

NSF Grant MET DMR-0241928, David N. Seidman, PI

Long-range solute-vacancy binding

LKMC 2[110]

[100]

[110]

[100]

[110]

[100]

[110]

[100]

The kinetic pathway of coarsening in a Ni-5.24at.%Al-14.24 at.%Cr alloy is strongly dependent on long-range solute-vacancy binding energies.

No long-range solute-vacancy binding

LKMC 1

Concentration profiles as a function of distance from the /’ interface, right-side. Experimental 3-D APT reconstructions follow LKMC 1 trajectories, which has long-range vacancy-solute binding energies out to fourth nearest neighbor.

LKMC 1 - coagulation-coalescence LKMC 2 - classic evaporation-condensation

Effects of Ru, Re, or W on Model Ni-base Superalloys (2)NSF Grant MET DMR-0241928, Northwestern University, David N. Seidman, PI

Dependence of Compositional Evolution at 800°C on Ru, Ru-Re, or Ru-Re-W additions

100 nm

10 nm

[110]

Ni-Cr-Al-Ru-Re-WNi-Cr-Al-Ru-ReNi-Cr-Al-Ru

Compositional evolution of ’-precipitates in Ni-8.5Cr-10Al-2Ru, Ni-8.5C5-10Al-1Ru-1Re and Ni-8.5C5-10Al-.5Ru-.5Re-1W (at.%) during aging at 800oC for up to 256 hours. Partitioning ratio, K, of an element is given by precipitate’s concentration of an element divided by matrix concentration the same element. Compositions measured by atom-probe analysis are all in atomic percent.

Effects of Ru, Re, or W on Model Ni-base Superalloys (1)NSF Grant MET DMR-0241928, Northwestern University, David N. Seidman, PI

Dependence of Precipitate Size Evolution at 800°C on Ru, Ru-Re, and Ru-Re-W additions

g = [111]

100 nm

10 nmCentered dark-field transmission electron microscopy (TEM) images of ’-precipitates in Ni-8.5Cr-10Al-2Ru, Ni-8.5C5-10Al-1Ru-1Re and Ni-8.5C5-10Al-.5Ru-.5Re-1W (at.%) after aging at 800oC for 4, 16, 64, or 256 hours (left-side), and comparison of stereologically corrected 3-D precipitate-size distributions (PSDs) with the predictions of the Akaiwa-Voorhees model1 for precipitated volume fractions of 20% (Ru-alloy) or 30% (Ru-Re and Ru-Re-W alloy)

[110]

4 h 16 h 64 h 256 h100nm

Ru

RuRe

RuReW

4 h 16 h 64 h 256 h

1Akaiwa, N. and Voorhees, P.W., Phys. Rev. E 49 (1994) 3860.