Abstract
The compositional and microstructural evolution of different generations of γ′ precipitates during the continuous cooling of a commercial nickel base superalloy, Rene88DT, has been characterized by three dimensional atom probe tomography coupled with energy-filtered transmission electron microscopy studies. After solutionizing in the single γ phase field, continuous cooling at a very high rate results in a monomodal size distribution of γ′ precipitates with a high nucleation density and non-equilibrium compositions. In contrast, a relatively slower cooling rate (∼ 24 °C/min) results in a multi-modal size distribution of γ′ precipitates with the larger first generation primary precipitates exhibiting close to equilibrium composition, along with the smaller scale secondary γ′ precipitates, exhibiting non-equilibrium composition (excess of Co and Cr, depleted in Al and Ti). The composition of the γ matrix near these precipitates also exhibits similar trends with the composition being closer to equilibrium near the primary precipitates as compared to the secondary precipitates.
Original language | English |
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Pages (from-to) | 878-886 |
Number of pages | 9 |
Journal | Materials Characterization |
Volume | 62 |
Issue number | 9 |
DOIs | |
State | Published - Sep 2011 |
Externally published | Yes |
Funding
The authors would like to acknowledge the US Air Force Research Laboratory (AFRL ISES contract) and the US Air Force Office of Scientific Research (AFOSR Grant # FA9550-06-1-0193 ) for providing financial support for this study. In addition, the authors also gratefully acknowledge the Center for Advanced Research and Technology (CART) at the University of North Texas and the Center for the Accelerated Maturation of Materials (CAMM) at the Ohio State University for access to the experimental facilities used for this study.
Keywords
- Atom probe tomography
- Energy-filtered transmission electron microscopy
- Gamma prime
- Nickel base superalloy