Atomic Scale Structure and Chemical Composition Across Order-Disorder Interfaces (POSTPRINT)
Abstract
The high strength of many metallic alloys, especially at elevated temperatures, including nickel base superalloys used in aircraft jet engines, is often attributed to the presence of homogeneously distributed second phase precipitates within a disordered matrix. In superalloys, the ordered precipitate/disordered matrix interface plays a critical role in determining the precipitate coarsening kinetics as well as the strengthening mechanism at high temperatures. Combining aberration-corrected high resolution scanning transmission electron microscopy (HRSTEM) with three-dimensional atom probe (3DAP) tomography, the atomic scale structure and chemical composition across the order/disorder interface in a nickel base superalloy has been determined. Experimentally, for the first time, the order-disorder transition across this interface has been shown to be approx. 4-6 atomic layers wide, while the compositional gradient across the same interface is approx. 12-14 atomic layers wide. Such atomic resolution information raises fundamental questions regarding the definition of such interfaces and is essential for understanding both their high temperature stability as well as role in strength.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2008
- Accession Number
- ADA504054
Entities
People
- Dennis M. Dimiduk
- G. B. Viswanathan
- H.L. Fraser
- J. Y. Hwang
- Jaimie S. Tiley
- R. Banerjee
- R. Srinivasan
Organizations
- Air Force Research Laboratory