ASTM E975-03

Standard Practice for X-Ray Determination of Retained Austenite in Steel with Near Random Crystallographic Orientation

SIGNIFICANCE AND USE
Significance—Retained austenite with a near random crystallographic orientation is found in the microstructure of heat-treated low-alloy, high-strength steels that have medium (0.40 weight %) or higher carbon contents. Although the presence of retained austenite may not be evident in the microstructure, and may not affect the bulk mechanical properties such as hardness of the steel, the transformation of retained austenite to martensite during service can affect the performance of the steel.
Use—The measurement of retained austenite can be included in low-alloy steel development programs to determine its effect on mechanical properties. Retained austenite can be measured on a companion sample or test section that is included in a heat-treated lot of steel as part of a quality control practice. The measurement of retained austenite in steels from service can be included in studies of material performance.
SCOPE
1.1 This practice covers the determination of retained austenite phase in steel using integrated intensities (area under peak above background) of X-ray diffraction peaks using chromium  K  or molybdenum K X-radiation.
1.2 The method applies to carbon and alloy steels with near random crystallographic orientations of both ferrite and austenite phases.
1.3 This practice is valid for retained austenite contents from 1 % by volume and above.
1.4 If possible, X-ray diffraction peak interference from other crystalline phases such as carbides should be eliminated from the ferrite and austenite peak intensities.
1.5 Substantial alloy contents in steel cause some change in peak intensities which have not been considered in this method. Application of this method to steels with total alloy contents exceeding 15 weight % should be done with care. If necessary, the users can calculate the theoretical correction factors to account for changes in volume of the unit cells for austenite and ferrite resulting from variations in chemical composition.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Oct-2003
• ICS: 77.080.20 - Steels
• Technical Committee: E04 - Metallography
• Drafting Committee: E04.11 - X-Ray and Electron Metallography

Relations

• Replaces: ASTM E975-00 - Standard Practice for X-Ray Determination of Retained Austenite in Steel with Near Random Crystallographic Orientation
• Effective Date: 01-Nov-2003
• Replaced By: ASTM E975-03(2008) - Standard Practice for X-Ray Determination of Retained Austenite in Steel with Near Random Crystallographic Orientation
• Effective Date: 01-Jun-2008

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E975–03
Standard Practice for
X-Ray Determination of Retained Austenite in Steel with
1
Near Random Crystallographic Orientation
This standard is issued under the fixed designation E975; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The volume percent of retained austenite (face-centered cubic phase) in steel is determined by
comparing the integrated chromium or molybdenum X-ray diffraction intensity of ferrite (bodycen-
tered cubic phase) and austenite phases with theoretical intensities. This method should be applied to
steelswithnearrandomcrystallographicorientationsofferriteandaustenitephasesbecausepreferred
crystallographicorientationscandrasticallychangethesemeasuredintensitiesfromtheoreticalvalues.
Chromium radiation was chosen to obtain the best resolution of X-ray diffraction peaks for other
crystalline phases in steel such as carbides. No distinction has been made between ferrite and
martensite phases because the theoretical X-ray diffraction intensities are nearly the same. Hereafter,
the term ferrite can also apply to martensite. This practice has been designed for unmodified
commercial X-ray diffractometers or diffraction lines on film read with a densitometer.
Other types of X-radiations such as cobalt or copper can be used, but most laboratories examining
ferrous materials use chromium radiation for improved X-ray diffraction peak resolution or
molybdenum radiation to produce numerous X-ray diffraction peaks. Because of special problems
associated with the use of cobalt or copper radiation, these radiations are not considered in this
practice.
1. Scope factors to account for changes in volume of the unit cells for
austenite and ferrite resulting from variations in chemical
1.1 This practice covers the determination of retained aus-
composition.
tenite phase in steel using integrated intensities (area under
1.6 This standard does not purport to address all of the
peak above background) of X-ray diffraction peaks using
safety concerns, if any, associated with its use. It is the
chromium K or molybdenum K X-radiation.
a a
responsibility of the user of this standard to establish appro-
1.2 The method applies to carbon and alloy steels with near
priate safety and health practices and determine the applica-
random crystallographic orientations of both ferrite and auste-
bility of regulatory limitations prior to use.
nite phases.
1.3 This practice is valid for retained austenite contents
2. Significance and Use
from 1% by volume and above.
2.1 Significance—Retained austenite with a near random
1.4 If possible, X-ray diffraction peak interference from
crystallographic orientation is found in the microstructure of
other crystalline phases such as carbides should be eliminated
heat-treated low-alloy, high-strength steels that have medium
from the ferrite and austenite peak intensities.
(0.40 weight%) or higher carbon contents. Although the
1.5 Substantial alloy contents in steel cause some change in
presence of retained austenite may not be evident in the
peak intensities which have not been considered in this
microstructure, and may not affect the bulk mechanical prop-
method. Application of this method to steels with total alloy
erties such as hardness of the steel, the transformation of
contents exceeding 15 weight% should be done with care. If
retained austenite to martensite during service can affect the
necessary, the users can calculate the theoretical correction
performance of the steel.
2.2 Use—The measurement of retained austenite can be
1
This practice is under the jurisdiction of ASTM Committee E04 on Metallog-
includedinlow-alloysteeldevelopmentprogramstodetermine
raphy and is the direct responsibility of Subcommittee E04.11 on X-Ray and
its effect on mechanical properties. Retained austenite can be
Electron Metallography.
measured on a companion sample or test section that is
Current edition approved Nov. 1, 2003. Published December 2003. Originally
approved in 1984. Last previous edition approved in 2000 as E975–00.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E975–03
A
TABLE 1 Calculated Theoretical Intensities Using Chromium K Radiation
a
2 B 2
hkl Sinu/lu f Df8 Df9 /F/ LP P T N R
(a iron, body-centered cubic, unit-cell dimension a = 2.8664Å):
o
B C
110 0.24669 34.41 18.474 −1.6 0.9 1142.2 4.290 12 0.9577 0.001803 101.5
B C
200 0.34887 53.06 15.218 −1.6 0.9 745.0 2.805 6 0.9172 0.001803 20.73
B C
211 0.42728 78.20 13.133 −1.6 0
...