Direct Atomic Scale Observation of the Structure and Chemistry of Order/Disorder Interfaces
Abstract
The high strength of many metallic alloys, including nickel base superalloys used in aircraft jet engines, especially at elevated temperatures, is often attributed to the presence of homogeneously distributed ordered intermetallic precipitates within a disordered matrix. The structure and chemistry at the precipitate/matrix interface plays a critical role in determining the effectiveness of the strengthening mechanism. Combining aberration-corrected high resolution scanning transmission electron microscopy (HRSTEM) with three-dimensional atom probe (3DAP) tomography the atomic scale structure and chemistry across the order/disorder interface in nickel base superalloys has been determined. While, the order/disorder interface is ~4 atomic layers thick, the width of the compositional gradient across the same interface is ~10 atomic layers thick. Such atomic resolution pictures of these interfaces raises fundamental questions regarding their definition and is essential for understanding both their high temperature stability as well as their role in strengthening by obstructing dislocation motion.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2008
- Accession Number
- ADA490077
Entities
People
- G. B. Viswanathan
- H.L. Fraser
- J. Y. Hwang
- Jaimie S. Tiley
- R. Banerjee
- R. Srinivasan
Organizations
- Air Force Research Laboratory