ASTM E7-00

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation:E7–00
Standard Terminology Relating to
Metallography
This standard is issued under the fixed designation E 7; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope properly use and interpret these standards, the terminology
used in these standards must be understood.
1.1 This standard covers the definition of terms, acronyms,
3.2 The terms used in the field of metallography have
and symbols used in ASTM documents related to the field of
precise definitions. The terminology and its proper usage must
metallography and metallographic testing. Terms that are only
be completely understood in order to adequately communicate
relevant to a particular standard or that are adequately defined
in this field. In this respect, this standard is also a general
in a general dictionary are not defined in this terminology
source of terminology relating to the field of metallography
standard.
facilitating the transfer of information within the field.
1.2 This standard includes terminology used in metallo-
graphic areas, such as, but not limited to: light microscopy,
4. Terminology
microindentation hardness testing, specimen preparation, x-ray
absorption—the decrease in intensity which radiation under-
and electron metallography, quantitative metallography, pho-
tomicrography, and determination of grain size and inclusion goes during its passage through matter when the ratio of
transmitted or reflected luminous flux to incident is less than
content.
1.3 This standard may be of use to individuals utilizing 1.
absorption coefficient—specific factor characteristic of a
standards of Committee E-4 as well as by those in need of a
general reference source for terminology in the field of substance on which its absorption radiation depends. The
rate of decrease of the natural logarithm of the intensity of a
metallography.
parallel beam per unit distance traversed in a substance. For
2. Referenced Documents
X-rays, the linear absorption coefficient is the natural loga-
2.1 ASTM Standards: rithm of the ratio of the incident intensity of an X-ray beam
E 14 Practice for Thermal Analysis of Metals and Alloys incident on unit thickness of an absorbing material to the
E 45 Test Methods for Determining the Inclusion Content intensity of the beam transmitted. If I is the incident inten-
e
of Steel sity of a beam of X-rays, I the transmitted intensity, and X
t
E 80 Practice for Dilatometric Analysis of Metallic Materi- the thickness of the absorbing material, then:
als
I 5 I exp~2μX! (1)
t e
E 92 Test Method for Vickers Hardness of Metallic Mate-
Here μ is the linear absorption coefficient. The mass absorption
rials
coefficient is given by μ/r where r is the density.
E 112 Test Methods for Determining Average Grain Size
absorption edge—an abrupt change in absorption coefficient
E 1122 Practice for Obtaining JK Inclusion Ratings Using
at a particular wavelength. The absorption coefficient is
Automatic Image Analysis
always larger on the short wavelength side of the absorption
edge.
3. Significance and Use
absorption limit—See absorption edge.
3.1 Standards of Committee E-4 consist of test methods,
accelerating potential—a relatively high voltage applied be-
practices, and guides developed to ensure proper and uniform
tween the cathode and anode of an electron gun to accelerate
testing in the field of metallography. In order for one to
electrons.
achromatic—literally, color-free. A lens or prism is said to be
This terminology is under the jurisdiction of ASTM Committee E04 on
achromatic when corrected for two colors. The remaining
Metallography and are the direct responsibility of Subcommittee E04.02 on
color seen in an image formed by such a lens is said to be
Metallographic Terminology and Nomenclature of Phase Diagrams.
Current edition approved July 10, 2000. Published September 2000. Originally secondary chromatic aberration. See apochromatic objec-
published as E7–26T. Last previous edition E 7 – 99b.
tive
Annual Book of ASTM Standards, Vol 04.01.
achromatic objective—an objective that is corrected chro-
Annual Book of ASTM Standards, Vol 03.01.
matically for two colors, and spherically for one, usually in
Discontinued; see 1984 Annual Book of ASTM Standards, Vol 14.02. Replaced
by E228.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E7
the yellow-green part of the spectrum. anode aperture—See aperture.
achromatic objective lens—an objective lens with longitudi- anvil—the base on which objects for hardness test are placed.
nal chromatic correction for green and blue, and spherical anvil effect—the effect caused by use of too high a load or
chromatic correction for green. Note—Lens should be used when testing the hardness of too thin a specimen, resulting in
with a green filter. a bulge or shiny spot on the under side of the specimen.
acid extraction—See extraction. aperture, electron:
air-lock—an intermediate enclosed chamber of a vacuum or anode aperture— the opening in the accelerating voltage
pressure system through which an object may be passed anode shield of the electron gun through which the electrons
without materially changing the vacuum or pressure of the must pass to illuminate or irradiate the specimen.
system. condenser aperture—an opening in the condenser lens
alignment—a mechanical or electrical adjustment of the controlling the number of electrons entering the lens and the
components of an optical device in such a way that the path angular aperture of the illuminating beam. The angular
of the radiating beam coincides with the optical axis or other aperture can also be controlled by the condenser lens current.
predetermined path in the system. In electron optics there are physical objective aperture—a metal diaphragm, centrally
three general types: pierced with a small hole, used to limit the cone of electrons
(1) magnetic alignment—an alignment of the electron accepted by the objective lens. This improves image contrast
optical axis of the electron microscope such that the image since highly scattered electrons are prevented from arriving
rotates about a point in the center of the viewing screen when at the Gaussian image plane and therefore can not contribute
the current flowing through a lens is varied. to background fog.
(2) mechanical alignment—a method of aligning the aperture, optical—the working diameter of a lens or a mirror.
geometrical axis of the electron microscope by relative angular aperture— the angle between the most divergent
physical movement of the components, usually as a step rays which can pass through a lens to form the image of an
preceding either magnetic or voltage alignment. object.
(3) voltage alignment—a condition of alignment of an aperture diaphragm—a device to define the aperture.
electron microscope such that the image expands or con- apochromatic objective—an objective with longitudinal chro-
tracts symmetrically about the center of the viewing screen matic correction for red, green and blue, and spherical
when the accelerating voltage is changed. chromatic correction for green and blue. This is the best
allotriomorphic crystal—a crystal whose lattice structure is choice for high resolution or color photomicrography.
normal, but whose outward shape is imperfect since it is arcing—in electron diffraction, the production of segments of
determined to some extent by the surroundings; the grains in circular patterns, indicating a departure from completely
a metallic aggregate are allotriomorphic crystals. random orientation of the crystals of the specimen.
alloy system—a complete series of compositions produced by arrest—that portion of a cooling curve in which temperature is
mixing in all proportions any group of two, or more, invariant with time (for example, thermal or eutectic arrest).
components, at least one of which is a metal. artifact—a false microstructural feature that is not an actual
alpha brass—a solid solution phase of one or more alloying characteristic of the specimen; it may be present as a result
elements in copper and having the same crystal lattice as of improper or inadequate preparation, handling methods, or
copper. optical conditions for viewing.
alpha iron (Fe)—solid phase of pure iron which is stable at ascending fork point—in a ternary phase diagram, the con-
temperatures below 910°C and possesses the body-centered figuration at the convergence of the three bivariant curves
cubic lattice. It is ferro-magnetic below 768°C. upon each of the four phases associated in Class II univariant
amplifier—a negative lens, used in lieu of an eyepiece, to equilibrium; for example, the union of two ascending liqui-
project under magnification the image formed by an objec- dus surface valleys to form one ascending liquidus surface
tive. The amplifier is especially designed for flatness of field valley.
and should be used with an apochromatic objective. aspect ratio—the length-to-width ratio of a microstructural
ampliphan eyepiece— See amplifier. feature in a two-dimensional plane.
analyzer—an optical device, capable of producing plane asterism—a lengthening of diffraction spots usually in the
polarized light, used for detecting the state of polarization. radial direction.
angle of reflection: ( 1) reflection—the angle between the astigmatism—a defect in a lens or optical system which
reflected beam and the normal to the reflecting surface. causes rays in one plane parallel to the optical axis to focus
(2) diffraction—the angle between the diffracted beam and at a distance different from those in the plane at right angles
the diffracting planes. to it.
Angstrom unit (abbreviation) = A,Å , or A. U—a unit of ASTM grain size number— See grain size.
−8
length equal to 10 cm. This is the standard unit of athermal—not isothermal, with changing rather than constant
measurement in X-ray crystallography. temperature conditions.
angular aperture—See aperture, optical. atomic replica—See replica.
anisotropic (replaces anisotropy)—having different values for atomic scattering factor—the ratio of the amplitude of the
a property, in different directions. wave scattered by an atom to that scattered by a single
annealing-twin bands— See twin bands. electron. Symbol = f.
E7
austenite—a face-centered cubic solid solution of carbon or by quenching austenite to a desired temperature and holding
other elements in gamma iron. for a period of time necessary for transformation to occur. If
austenite grain size—the grain size which exists or existed in the transformation temperature is just below that at which
austenite at a given temperature. See Test Methods E 112. the finest pearlite is formed, the bainite (upper bainite) has a
autographic dilatometer—a dilatometer that automatically feathery appearance. If the transformation temperature is just
records instantaneous and continuous changes in dimensions above that at which martensite is produced, the bainite
and some other controlled variable such as temperature or (lower bainite) is acicular, resembling slightly tempered
time. martensite. At the higher resolution of the electron micro-
autographic pyrometer— See pyrometer. scope, upper bainite is observed to consist of plates of
automatic image analysis—the separation and quantitative cementite in a matrix of ferrite. These discontinuous carbide
evaluation of an image into its elements with or without plates tend to have parallel orientation in the direction of the
operator interaction. It includes the enhancement, detection, longer dimension of the bainite areas. Lower bainite consists
and quantification of the features contained in an image of ferrite needles containing carbide platelets in parallel
through the use of optical, geometrical, and stereological array cross-striating each needle axis at an angle of about
parameters and a computer program. Image analysis data 60°. Intermediate bainite resembles upper bainite; however,
output can provide individual measurements on each sepa- the carbides are smaller and more randomly oriented.
rate feature (feature specific) or totals for all features of a balanced filters (X-rays)—a pair of filters used to eliminate
particular type in the field (field specific). all but a narrow range of wavelengths. The filter materials
automatic image analyzer—a device which can be pro- and thicknesses are chosen so that their absorption edges lie
grammed to detect and measure features of interest in an very close together and so that they have the same absorption
image. It may include accessories such as automatic focus except for wavelengths lying in the range between their
and an automatic traversing stage to permit unattended absorption edges. When these filters are used alternately, the
operation. difference in effect, if any, is due to X-rays that have
average coefficient of cubical expansion— average change in wavelengths in this range. Balanced filters thus can be made
unit volume of a substance per unit change in temperature to serve as a crude monochromator.
over a specified range of temperature. band—in electron diffraction, a broad intensity maximum with
average coefficient of linear expansion— average change in sharp edges.
unit length of a body per unit change in temperature over a banded structure (banding)—alternate bands parallel with
specified range of temperature. the direction of working resulting from the elongation of
average coefficient of thermal expansion— general term. segregated areas.
(See also average coefficient of cubical expansion and barrel distortion— See distortion.
average coefficient of linear expansion.) basal plane—that plane of a hexagonal or tetragonal crystal
average grain diameter— See grain size. which is perpendicular to the axis of highest symmetry. Its
axial ratio—the ratio of the length of one axis to that of Miller indices are (0001) or (001), respectively.
another (for example, c/a) or the continued ratio of three bellows length—the distance from the eyepiece to the photo-
axes (for example, a:b:c). sensitive material or viewing screen in a photomicrographic
axis (crystal)—the edge of the unit cell of a space lattice. Any apparatus.
one axis of any one lattice is defined, in length and direction, Bertrand lens—an auxiliary removable lens in the body of a
with respect to the other axes of that lattice. microscope, used to examine images in the back focal plane
Babo’s law—the vapor press
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