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Title: Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography

In this study, the analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L12-ordered g precipitates to form Ni3(Al,Cr) precipitates in a Ni-14Al-7Cr(at.%) alloy. Interestingly, the addition of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within g precipitates to form (Ni,Al)3(Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Univ. of North Texas, Denton, TX (United States)
  2. Air Force Research Lab., Dayton, OH (United States)
Publication Date:
OSTI Identifier:
1241481
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Ultramicroscopy
Additional Journal Information:
Journal Volume: 159; Journal Issue: P2; Journal ID: ISSN 0304-3991
Publisher:
Elsevier
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE nickel-base superalloys; APT; EBSD; site occupancy; SDM