STEM imaging of prior austenite grain boundaries[Scanning Transmission Electron Microscopy]

Journal Article · Fri Mar 17 04:00:00 EST 2000 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(99)00399-1· OSTI ID:20050490

Papworth, A J; Williams, D B

The problem of temper embrittlement of low-alloy steels used in steam-turbine generators was thought to have been solved by the introduction of clean steels with low levels of certain impurities. However, even these steels exhibit temper embrittlement at turbine operation temperatures >400 C. Initial studies of temper embrittlement of clean steels used Auger electron spectrometry (AES) of fracture surfaces. The failure was found to occur along the prior austenite grain boundaries (PAGBs) where P segregation was found. A better way to relate P segregation to boundary crystallography is to use the analytical scanning transmission electron microscopy (STEM) since, in this technique, the boundaries are not fractured and direct comparison can be made between the boundary chemistry and the crystallography. Clean steels have a very large variation in precipitation densities often making density measurements impossible, diffraction contrast is poor in the STEM image and etching may change the boundary chemistry. This paper presents an alternative simple method to identify the PAGB in a STEM prior to chemical and crystallographic analysis.

• Research Organization: Lehigh Univ., Bethlehem, PA (US)
• OSTI ID: 20050490
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 7 Vol. 42; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AUSTENITE
EMBRITTLEMENT
GRAIN BOUNDARIES
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
SEGREGATION
STEEL-NICRMO