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The Influence of Tungsten on the Chemical Composition of a Temporally Evolving Nanostructure of a Model Ni-Al-Cr SuperalloyThe influence of W on the temporal evolution of gamma' precipitation toward equilibrium in a model Ni-Al-Cr alloy is investigated by three-dimensional atom-probe (3DAP) microscopy and transmission electron microscopy (TEM). We report on the alloys Ni-10 Al-8.5 Cr (at.%) and Ni-10 Al-8.5 Cr-2 W (at.%), which were aged isothermally in the gamma + gamma' two-phase field at 1073 K, for times ranging from 0.25 to 264 h. Spheroidal-shaped gamma' precipitates, 5-15 nm diameter, form during quenching from above the solvus temperature in both alloys at a high number density (approx. 10(exp 23/cu m). As gamma' precipitates grow with aging at 1073 K, a transition from spheriodal- to cuboidal-shaped precipitates is observed in both alloys. The elemental partitioning and spatially resolved concentration profiles across the gamma' precipitates are obtained as a function of aging time from three-dimensional atom-by-atom reconstructions. Proximity histogram concentration profiles of the quaternary alloy demonstrate that W concentration gradients exist in gamma' precipitates in the as-quenched and 0.25-h aging states, which disappear after 1 h of aging. The diffusion coefficient of W in gamma' is estimated to be 6.2 x 10(exp -20) sq m/s at 1073 K. The W addition decreases the coarsening rate constant, and leads to stronger partitioning of Al to gamma' and Cr to gamma.
Document ID
20050198864
Acquisition Source
Glenn Research Center
Document Type
Reprint (Version printed in journal)
Authors
Sudbrack, Chantal K.
(Northwestern Univ. Evanston, IL, United States)
Isheim, Dieter
(Northwestern Univ. Evanston, IL, United States)
Noebe, Ronald D.
(NASA Glenn Research Center Cleveland, OH, United States)
Jacobson, Nathan S.
(NASA Glenn Research Center Cleveland, OH, United States)
Seidman, David N.
(Northwestern Univ. Evanston, IL, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2004
Publication Information
Publication: Microscopy and Microanalysis
Publisher: Microscopy Society of America
Volume: 10
Subject Category
Metals And Metallic Materials
Report/Patent Number
E-14859
Funding Number(s)
WBS: WBS 22-708-04-03-05
CONTRACT_GRANT: NSF DMR-97-28986
Distribution Limits
Public
Copyright
Other

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