Moessbauer study of austenite stability and impact fracture in Fe--6Ni steel

Technical Report · Thu Jun 01 04:00:00 EDT 1978

DOI:https://doi.org/10.2172/6672630· OSTI ID:6672630

Fultz, B T

The two phase (..cap alpha.. + ..gamma..) microstructure of a commercial cryogenic alloy steel was studied with regard to possible phase transformations induced by impact fracture. A backscatter Moessbauer spectrometer was constructed for measurements of atomic fractions of the two phases near specimen surfaces. Moessbauer spectra were collected from several types of unpolished and chemically polished surfaces of impact specimens to reveal (for the first time) the depth profile of the observed ..gamma.. ..-->.. ..cap alpha..' transformation near fracture surfaces. It was found that the spatial extent of transformation could be monotonically related to the impact energy absorbed by the specimen. These results are interpreted in light of several models of phase stability and impact toughness. A general description of the Moessbauer effect and methods of spectral analysis is included. The method of linear perturbations in the hyperfine magnetic field is discussed with respect to its general usefulness in obtaining chemical information for Moessbauer spectra of the ..cap alpha.. phase. The procedure adopted for spectral analysis was chosen to provide an accurate phase analysis at the expense of chemical information. Both the Moessbauer equipment and analysis procedures were developed with the primary objective of providing a routine metallurgical phase analysis technique for low alloy steels.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6672630
• Report Number(s): LBL-7671
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
AUSTENITIC STEELS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
EVEN-ODD NUCLEI
FRACTURE PROPERTIES
HYPERFINE STRUCTURE
INTERMEDIATE MASS NUCLEI
IRON 57
IRON ALLOYS
IRON BASE ALLOYS
IRON ISOTOPES
ISOTOPES
MECHANICAL PROPERTIES
MICROSTRUCTURE
MOESSBAUER EFFECT
NICKEL ALLOYS
NICKEL STEELS
NUCLEI
PHASE TRANSFORMATIONS
STABILITY
STABLE ISOTOPES
STEELS