Accession Number:

ADA504054

Title:

Atomic Scale Structure and Chemical Composition Across Order-Disorder Interfaces (POSTPRINT)

Descriptive Note:

Journal article postprint

Corporate Author:

AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE

Report Date:

2008-07-01

Pagination or Media Count:

6.0

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 precipitatedisordered 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 orderdisorder 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.

Subject Categories:

  • Physical Chemistry
  • Properties of Metals and Alloys
  • Test Facilities, Equipment and Methods
  • Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE