ASTM E3-01(2007)e1
(Practice)Standard Guide for Preparation of Metallographic Specimens
Standard Guide for Preparation of Metallographic Specimens
SIGNIFICANCE AND USE
Microstructures have a strong influence on the properties and successful application of metals and alloys. Determination and control of microstructure requires the use of metallographic examination.
Many specifications contain a requirement regarding microstructure; hence, a major use for metallographic examination is inspection to ensure that the requirement is met. Other major uses for metallographic examination are in failure analysis, and in research and development.
Proper choice of specimen location and orientation will minimize the number of specimens required and simplify their interpretation. It is easy to take too few specimens for study, but it is seldom that too many are studied.
SCOPE
1.1 The primary objective of metallographic examinations is to reveal the constituents and structure of metals and their alloys by means of a light optical or scanning electron microscope. In special cases, the objective of the examination may require the development of less detail than in other cases but, under nearly all conditions, the proper selection and preparation of the specimen is of major importance. Because of the diversity in available equipment and the wide variety of problems encountered, the following text presents for the guidance of the metallographer only those practices which experience has shown are generally satisfactory; it cannot and does not describe the variations in technique required to solve individual specimen preparation problems.
Note 1—For a more extensive description of various metallographic techniques, refer to Samuels, L. E., Metallographic Polishing by Mechanical Methods, American Society for Metals (ASM) Metals Park, OH, 3rd Ed., 1982; Petzow, G., Metallographic Etching, ASM, 1978; and VanderVoort, G., Metallography: Principles and Practice, McGraw Hill, NY, 2nd Ed., 1999.
1.2 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.
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´1
Designation:E3–01 (Reapproved 2007)
Standard Guide for
Preparation of Metallographic Specimens
This standard is issued under the fixed designation E3; 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.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Section 13, Precision and Bias was editorially removed from the standard in March 2009.
1. Scope E340 Test Method for Macroetching Metals and Alloys
E407 Practice for Microetching Metals and Alloys
1.1 The primary objective of metallographic examinations
E768 Guide for Preparing and Evaluating Specimens for
is to reveal the constituents and structure of metals and their
Automatic Inclusion Assessment of Steel
alloys by means of a light optical or scanning electron
E1077 Test Methods for Estimating the Depth of Decarbur-
microscope. In special cases, the objective of the examination
ization of Steel Specimens
may require the development of less detail than in other cases
E1122 Practice for Obtaining JK Inclusion Ratings Using
but, under nearly all conditions, the proper selection and
Automatic Image Analysis
preparationofthespecimenisofmajorimportance.Becauseof
E1245 Practice for Determining the Inclusion or Second-
the diversity in available equipment and the wide variety of
Phase Constituent Content of Metals by Automatic Image
problems encountered, the following text presents for the
Analysis
guidance of the metallographer only those practices which
E1268 Practice for Assessing the Degree of Banding or
experience has shown are generally satisfactory; it cannot and
Orientation of Microstructures
does not describe the variations in technique required to solve
E1558 Guide for Electrolytic Polishing of Metallographic
individual specimen preparation problems.
Specimens
NOTE 1—For a more extensive description of various metallographic
E1920 Guide for Metallographic Preparation of Thermal
techniques,refertoSamuels,L.E., Metallographic Polishing by Mechani-
Sprayed Coatings
cal Methods, American Society for Metals (ASM) Metals Park, OH, 3rd
Ed., 1982; Petzow, G., Metallographic Etching, ASM, 1978; and Vander-
3. Terminology
Voort, G., Metallography: Principles and Practice,McGrawHill,NY,2nd
3.1 Definitions:
Ed., 1999.
3.1.1 For definitions used in this practice, refer to Termi-
1.2 This standard does not purport to address all of the
nology E7.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 castable mount—a metallographic mount generally
priate safety and health practices and determine the applica-
made from a two component castable plastic. One component
bility of regulatory limitations prior to use.
is the resin and the other hardener. Both components can he
liquid or one liquid and a powder. Castable mounts generally
2. Referenced Documents
do not require heat and pressure to cure.
2.1 ASTM Standards:
3.2.2 compression mount—a metallographic mount made
A90/A90M Test Method for Weight [Mass] of Coating on
using plastic that requires both heat and pressure for curing.
Iron and Steel Articles with Zinc or Zinc-Alloy Coatings
3.2.3 planar grinding—is the first grinding step in a prepa-
E7 Terminology Relating to Metallography
ration procedure used to bring all specimens into the same
E45 Test Methods for Determining the Inclusion Content of
plane of polish. It is unique to semi or fully automatic
Steel
preparation equipment that utilize specimen holders.
3.2.4 rigid grinding disc—a non-fabric support surface,
ThisguideisunderthejurisdictionofASTMCommitteeE04onMetallography such as a composite of metal/ceramic or metal/polymer
and is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.
Current edition approved July 1, 2007. Published September 2007. Originally
approved in 1921. Last previous edition approved in 2001 as E3 – 01. DOI: Withdrawn. The last approved version of this historical standard is referenced
10.1520/E0003-01R07E01. on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
E3–01 (2007)
charged with an abrasive (usually 6 to 15µm diamond par- 5.3 Transverse sections or cross sections taken perpendicu-
ticles), and used as the fine grinding operation in a metallo- lar to the main axis of the material are often used for revealing
graphic preparation procedure. the following information:
5.3.1 Variations in structure from center to surface,
4. Significance and Use
5.3.2 Distribution of nonmetallic impurities across the sec-
4.1 Microstructures have a strong influence on the proper-
tion,
ties and successful application of metals and alloys. Determi-
5.3.3 Decarburization at the surface of a ferrous material
nation and control of microstructure requires the use of
(see Test Method E1077),
metallographic examination.
5.3.4 Depth of surface imperfections,
4.2 Many specifications contain a requirement regarding
5.3.5 Depth of corrosion,
microstructure; hence, a major use for metallographic exami-
5.3.6 Thickness of protective coatings, and
nationisinspectiontoensurethattherequirementismet.Other
5.3.7 Structure of protective coating. See Guide E1920.
major uses for metallographic examination are in failure
5.4 Longitudinal sections taken parallel to the main axis of
analysis, and in research and development.
the material are often used for revealing the following infor-
4.3 Proper choice of specimen location and orientation will
mation:
minimize the number of specimens required and simplify their 5.4.1 Inclusion content of steel (see Practices E45, E768,
interpretation. It is easy to take too few specimens for study,
E1122, and E1245),
but it is seldom that too many are studied. 5.4.2 Degree of plastic deformation, as shown by grain
distortion,
5. Selection of Metallographic Specimens
5.4.3 Presence or absence of banding in the structure (see
5.1 The selection of test specimens for metallographic
Practice E1268), and
examination is extremely important because, if their interpre-
5.4.4 The microstructure attained with any heat treatment.
tationistobeofvalue,thespecimensmustberepresentativeof
5.5 The locations of surfaces examined should always be
the material that is being studied. The intent or purpose of the
giveninreportingresultsandinanyillustrativemicrographs.A
metallographic examination will usually dictate the location of
suitablemethodofindicatingsurfacelocationsisshowninFig.
the specimens to be studied. With respect to purpose of study,
1.
metallographic examination may be divided into three classi-
6. Size of Metallographic Specimens
fications:
5.1.1 General Studies or Routine Work—Specimens should
6.1 For convenience, specimens to be polished for metallo-
be chosen from locations most likely to reveal the maximum
graphicexaminationaregenerallynotmorethanabout12to25
variations within the material under study. For example,
specimens could be taken from a casting in the zones wherein
maximum segregation might be expected to occur as well as
specimens from sections where segregation could be at a
minimum. In the examination of strip or wire, test specimens
could be taken from each end of the coils.
5.1.2 Study of Failures—Test specimens should be taken as
closely as possible to the fracture or to the initiation of the
failure. Before taking the metallographic specimens, study of
the fracture surface should be complete, or, at the very least,
the fracture surface should be documented. In many cases,
specimens should be taken from a sound area for a comparison
of structures and properties.
5.1.3 Research Studies—The nature of the study will dictate
specimen location, orientation, etc. Sampling will usually be
more extensive than in routine examinations.
5.2 Having established the location of the metallographic
samples to be studied, the type of section to be examined must
Symbol in
Suggested Designation
be decided.
Diagram
5.2.1 For a casting, a section cut perpendicular to the
surfacewillshowthevariationsinstructurefromtheoutsideto A Rolled surface
B Direction of rolling
the interior of the casting.
C Rolled edge
5.2.2 In hot-worked or cold-worked metals, both transverse
D Planar section
and longitudinal sections should be studied. Special investiga-
E Longitudinal section perpendicular to rolled surface
tions may require specimens with surfaces prepared parallel to
F Transverse section
the original surface of the product.
G Radial longitudinal section
5.2.3 In the case of wire and small rounds, a longitudinal H Tangential longitudinal section
section through the center of the specimen proves advanta-
FIG. 1 Method of Designating Location of Area Shown in
geous when studied in conjunction with the transverse section. Photomicrograph.
´1
E3–01 (2007)
mm (0.5 to 1.0 in.) square, or approximately 12 to 25 mm in cutting operations produce some depth of damage, which will
diameter if the material is cylindrical. The height of the have to be removed in subsequent preparation steps.
specimen should be no greater than necessary for convenient
handling during polishing. 8. Cleanliness
6.1.1 Larger specimens are generally more difficult to pre-
8.1 Cleanliness (see Appendix X1) during specimen prepa-
pare.
ration is essential. All greases, oils, coolants and residue from
6.1.2 Specimens that are, fragile, oddly shaped or too small
cutoff blades on the specimen should be removed by some
to be handled readily during polishing should be mounted to
suitable organic solvent. Failure to clean thoroughly can
ensure a surface satisfactory for microscopical study. There
prevent cold mounting resins from adhering to the specimen
are, based on technique used, three fundamental methods of
surface. Ultrasonic cleaning may be effective in removing the
mounting specimens (see Section 9).
last traces of residues on a specimen surface.
8.2 Any coating metal that will interfere with the subse-
7. Cutting of Metallographic Specimens
quent etching of the base metal should be removed before
7.1 In cutting the metallographic specimen from the main
polishing, if possible. If etching is required, when studying the
body of the material, care must be exercised to minimize
underlying steel in a galvanized specimen, the zinc coating
altering the structure of the metal. Three common types of
should be removed before mounting to prevent galvanic effects
sectioning are as follows:
during etching. The coating can be removed by dissolving in
7.1.1 Sawing, whether by hand or machine with lubrication,
cold nitric acid (HNO , sp gr 1.42), in dilute sulfuric acid
is easy, fast, and relatively cool. It can be used on all materials
(H SO ) or in dilute hydrochloric acid (HCl). The HNO
2 4 3
with hardnesses below approximately 350 HV. It does produce
method requires care to prevent overheating, since large
a rough surface containing extensive plastic flow that must be
samples will generate considerable heat. By placing the clean-
removed in subsequent preparation.
ing container in cold water during the stripping of the zinc,
7.1.2 An abrasive cut-off blade will produce a smooth
attack on the underlying steel will be minimized. More
surfaceoftenreadyforfinegrinding.Thismethodofsectioning
information may be found in Test Method A90/A90M.
is normally faster than sawing. The choice of cut-off blade,
NOTE 2—Picral etchant produces little or no galvanic etching effects
lubricant, cooling conditions, and the grade and hardness of
when used on galvanized steel.
metal being cut will influence the quality of the cut. A poor
NOTE 3—The addition of an inhibitor during the stripping of Zn from
choice of cutting conditions can easily damage the specimen,
galvanized coatings will minimize the attack of the steel substrate. NEP
producing an alteration of the microstructure. Generally, soft
(polethylinepolyamine) or SbCl are two useful inhibitors.
materials are cut with a hard bond blade and hard materials
with a soft bond blade. Aluminum oxide abrasive blades are 8.3 Oxidized or corroded surfaces may be cleaned as
preferred for ferrous metals and silicon carbide blades are described in Appendix X1.
preferred for nonferrous alloys. Abrasive cut-off blades are
essential for sectioning metals with hardness above about 350 9. Mounting of Specimens
HV. Extremely hard metallic materials and ceramics may be
9.1 There are many instances where it will be advantageous
more effectively cut using diamond-impregnated cutting
to mount the specimen prior to grinding and polishing. Mount-
blades. Manufacturer’s instructions should be followed as to
ing of the specimen is usually performed on small, fragile, or
thechoiceofblade.Table1liststhesuggestedcutoffbladesfor
oddly shaped specimens, fractures, or in instances where the
materials with various Vickers (HV) hardness values.
specimen edges are to be examined.
7.1.3 Ashear is a type of cutting tool with which a material
9.2 Specimens may be either mechanically mounted,
in the form of wire, sheet, plate or rod is cut between two
mounted in plastic, or a combination of the two.
opposing blades.
9.3 Mechanical Mounting:
7.2 Othermethodsofsectioningarepermittedprovidedthey
9.3.1 Strip and sheet specimens may be mounted by binding
do not alter the microstructure at the plane of polishing. All
orclampingseveralspecimensintoapackheldtogetherbytwo
end pieces and two bolts.
TABLE 1 Cutoff Blade Selection
9.3.2 The specimens should be tightly bound together to
Hardness HV Materials Abrasive Bond Bond Hardness
prevent absorption and subsequent exudation of polishing
up to 300 non-ferrous (Al, Cu) SiC P or R hard
materials or etchants.
up to 400 non-ferrous (Ti) SiC P or R med. hard
9.3.3 The use of filler sheets of a softer material alternated
up to 400 soft ferrous Al O P or R hard
2 3
with the specimen may be used in order to minimize the
up to 500 medium soft ferrous Al O P or R med. hard
2 3
up to 600 medium hard ferrous Al O P or R medium
2 3 seepage of polishing materials and etchants. Use of filler
up to 700 hard ferrous Al O P or R&R med. soft
2 3
material is especially advantageous if the specimens have a
up to 800 very hard ferrous Al O P or R&R soft
2 3
high degree of surface irregularities.
> 800 extremely hard ferrous CBN P or M hard
more brittle ceramics diamond P or M very hard
9.3.4 Filler material must be chosen so as not to react
tougher ceramics diamond M ext. hard
electrolytically with th
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
An American National Standard
Designation:E3–95
StandardStandard GuidePracticeforfor Designation:E3–01 (Reapproved
´1
2007)Preparation of Metallographic Specimens
This standard is issued under the fixed designation E 3; 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.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Section 13, Precision and Bias was editorially removed from the standard in March 2009.
1. Scope
1.1 The primary objective of metallographic examinations is to reveal the constituents and structure of metals and their alloys
by means of thea light optical or scanning electron microscope. In special cases, the objective of the examination may require the
development of less detail than in other cases but, under nearly all conditions, the proper selection and preparation of the specimen
is of major importance. Because of the diversity in available equipment and the wide variety of problems encountered, the
following text presents for the guidance of the metallographer only those practices which experience has shown are generally
satisfactory;itcannotanddoesnotdescribethevariationsintechniquerequiredtosolveindividualspecimenpreparationproblems.
NOTE 1—For a more extensive description of various metallographic techniques, refer to Samuels, L. E., Metallographic Polishing by Mechanical
Methods, American Society for Metals (ASM) Metals Park, OH, 3rd Ed., 1982; Petzow, G., Metallographic Etching, ASM, 1978; and VanderVoort, G.,
Metallography: Principles and Practice , McGraw Hill, NY, 1984. , McGraw Hill, NY, 2nd Ed., 1999.
1.2 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.
2. Referenced Documents
2.1 ASTM Standards:
E7Terminology Relating to Metallography
A 90/A 90M Test Method for Weight [Mass] of Coating on Iron and Steel Articles with Zinc or Zinc-Alloy Coatings
E7 Terminology Relating to Metallography
E45 Practice Test Methods for Determining the Inclusion Content of Steel
E 340 Test Method for Macroetching Metals and Alloys
E 407 Test Methods Practice for Microetching Metals and Alloys
E 768 Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel
E 1077 Test Methods for Estimating the Depth of Decarburization of Steel Specimens
E 1122 Practice for Obtaining JK Inclusion Ratings Using Automatic Image Analysis
E 1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis
E 1268 Practice for Assessing the Degree of Banding or Orientation of Microstructures
E 1558 Guide to Electrolytic Polishing of Metallographic Specimens Guide for Electrolytic Polishing of Metallographic
Specimens
E 1920 Guide for Metallographic Preparation of Thermal Sprayed Coatings
3. Significance and Use
3.1Microstructures have a strong influence on the properties and successful application of metals and alloys. Determination and
control of microstructure requires the use of metallographic examination.
3.2Many specifications contain a requirement regarding microstructure; hence, a major use for metallographic examination is
inspection to ensure that the requirement is met. Other major uses for metallographic examination are in failure analysis, and in
research and development.
This practice is under the jurisdiction of ASTM Committee E-4 on Metallography and is the direct responsibility of Subcommittee E04.01 on Sampling, Specimen
Preparation, and Photography.
Current edition approved Jan. 15, 1995. Published March 1995. Originally published as E3–21T. Last previous edition E3–80 (1986).
This guide is under the jurisdiction of ASTM Committee E04 on Metallography and is the direct responsibility of Subcommittee E04.01 on Specimen Preparation .
Current edition approved July 1, 2007. Published September 2007. Originally approved in 1921. Last previous edition approved in 2001 asE3–01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
E3–01 (2007)
3.3Proper choice of specimen location and orientation will minimize the number of specimens required and simplify their
interpretation. It is easy to take too few specimens for study, but it is seldom that too many are studied. Terminology
3.1 Definitions:
3.1.1 For definitions used in this practice, refer to Terminology E 7.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 castable mount—a metallographic mount generally made from a two component castable plastic. One component is the
resin and the other hardener. Both components can he liquid or one liquid and a powder. Castable mounts generally do not require
heat and pressure to cure.
3.2.2 compression mount—a metallographic mount made using plastic that requires both heat and pressure for curing.
3.2.3 planar grinding—is the first grinding step in a preparation procedure used to bring all specimens into the same plane of
polish. It is unique to semi or fully automatic preparation equipment that utilize specimen holders.
3.2.4 rigid grinding disc—a non-fabric support surface, such as a composite of metal/ceramic or metal/polymer charged with
an abrasive (usually 6 to 15µm diamond particles), and used as the fine grinding operation in a metallographic preparation
procedure.
4. Significance and Use
4.1 Microstructureshaveastronginfluenceonthepropertiesandsuccessfulapplicationofmetalsandalloys.Determinationand
control of microstructure requires the use of metallographic examination.
4.2 Many specifications contain a requirement regarding microstructure; hence, a major use for metallographic examination is
inspection to ensure that the requirement is met. Other major uses for metallographic examination are in failure analysis, and in
research and development.
4.3 Proper choice of specimen location and orientation will minimize the number of specimens required and simplify their
interpretation. It is easy to take too few specimens for study, but it is seldom that too many are studied.
5. Selection of Metallographic Specimens
4.1The5.1 Theselectionoftestspecimensformetallographicexaminationisextremelyimportantbecause,iftheirinterpretation
is to be of value, the specimens must be representative of the material that is being studied. The intent or purpose of the
metallographic examination will usually dictate the location of the specimens to be studied. With respect to purpose of study,
metallographic examination may be divided into three classifications:
4.1.15.1.1 General Studies or Routine Work—Specimens from locations that are — Specimens should be chosen from locations
most likely to reveal the maximum variations within the material under study should be chosen. study. For example, specimens
shouldcould be taken from a casting in the zones wherein maximum segregation might be expected to occur as well as specimens
from sections where segregation shouldcould be at a minimum. In the examination of strip or wire, test specimens shouldcould
be taken from each end of the coils.
4.1.25.1.2 Study of Failures—Test specimens should be taken as closely as possible to the fracture or to the initiation of the
failure. Before taking the metallographic specimens, study of the fracture surface should be complete, or, at the very least, the
fracture surface should be documented. Specimens In many cases, specimens should be taken in many cases from a sound area
for a comparison of structures and properties.
4.1.35.1.3 Research Studies—The nature of the study will dictate specimen location, orientation, etc. Sampling will usually be
more extensive than in routine examinations.
45.2 Having established the location of the metallographic samples to be studied, the type of section to be examined must be
decided.
5.2.1 Foracasting,asectioncutperpendiculartothesurfacewillshowthevariationsinstructurefromtheoutsidetotheinterior
of the casting.
5.2.2 In hot-worked or cold-worked metals, both transverse and longitudinal sections should be studied. Special investigations
may at times require specimens with surfaces prepared parallel to the original surface of the product.
5.2.3 In the case of wire and small rounds, a longitudinal section through the center of the specimen proves advantageous when
studied in conjunction with the transverse section.
4.3Cross5.3 Transverse sections or transversecross sections taken perpendicular to the main axis of the material are more
suitableoften used for revealing the following information:
45.3.1 Variations in structure from center to surface,
45.3.2 Distribution of nonmetallic impurities across the section,
45.3.3 Decarburization at the surface of a ferrous material (see Test Method E 1077),
4.3.4Depth of surface imperfections,
4.3.5Depth of corrosion,
4.3.6Thickness of protective coatings, and
4.3.7Structure of protective coating.
4.4Longitudinalsectionstakenparalleltothemainaxisofthematerialaremoresuitableforrevealingthefollowinginformation:
4.4.1Inclusion content of steel (see Practice E45
´1
E3–01 (2007)
5.3.4 Depth of surface imperfections,
5.3.5 Depth of corrosion,
5.3.6 Thickness of protective coatings, and
5.3.7 Structure of protective coating. See Guide E 1920.
5.4 Longitudinal sections taken parallel to the main axis of the material are often used for revealing the following information:
5.4.1 Inclusion content of steel (see Practices E 45, E 768, E 1122, and E 1245),
45.4.2 Degree of plastic deformation, as shown by grain distortion,
45.4.3 Presence or absence of banding in the structure (see Practice E 1268), and
4.4.4The quality5.4.4 The microstructure attained with any heat treatment.
4.5The5.5 The locations of surfaces examined should always be given in reporting results and in any illustrative micrographs.
A suitable method of indicating surface locations is shown in Fig. 1.
5.
6. Size of Metallographic Specimens
5.1The specimens to be polished for metallographic examination are generally not more than about 12 to 25 mm (0.5 to 1.0 in.)
square, or approximately 12 to 25 mm in diameter if the material is round. The height of the specimen should be no greater than
necessary for convenient handling during polishing.
5.2It is not always possible to secure specimens having the dimensions given in 5.1, when the material to be examined is smaller
than the ideal dimensions. For example, in the polishing of wire, strip, and other small articles, it is necessary to mount the
specimens because of their size and shape.
5.2.1Larger samples may be mounted or not, as the available equipment dictates. However, the larger the specimen, the more
difficult it is to prepare, especially by manual methods.
5.2.2Specimens that are too small to be handled readily during polishing should be mounted to ensure a surface satisfactory for
microscopical study. There are, based on technique used, three fundamental methods of mounting specimens (see Sections 7-9
6.1 For convenience, specimens to be polished for metallographic examination are generally not more than about 12 to 25 mm
(0.5 to 1.0 in.) square, or approximately 12 to 25 mm in diameter if the material is cylindrical. The height of the specimen should
be no greater than necessary for convenient handling during polishing.
Symbol in
Suggested Designation
Diagram
A Rolled surface
B Direction of rolling
C Rolled edge
D Longitudinal (or lengthwi se) section parallel to rolled sur-
face
D Planar section
E Longitudinal section perpendicular to rolled surface
F Transverse section
G Radial longitudinal section
H Tangential longitudinal section
FIG. 1 Method of Designating Location of Area Shown in
Photomicrograph.
´1
E3–01 (2007)
6.1.1 Larger specimens are generally more difficult to prepare.
6.1.2 Specimens that are, fragile, oddly shaped or too small to be handled readily during polishing should be mounted to ensure
a surface satisfactory for microscopical study. There are, based on technique used, three fundamental methods of mounting
specimens (see Section 9).
6.
7. Cutting of Metallographic Specimens
6.1In7.1 Incuttingthemetallographicspecimenfromthemainbodyofthematerial,caremustbeexercisedtominimizealtering
the structure of the metal. Three common types of sectioning are as follows:
67.1.1 Sawing, whether by hand or machine with lubrication, is easy and easy, fast, and relatively cool. It can be used on all
materials with hardnesses below approximately 35 HRC.350 HV. It does produce a rough surface containing extensive plastic flow
that must be removed in subsequent preparation.
6.1.2An7.1.2 An abrasive cut-off wheelblade will produce a smooth surface often ready for fine grinding. This method of
sectioning is normally faster than sawing. The choice of cut-off wheel,blade, lubricant, cooling conditions, and the grade and
hardness of metal being cut will influence the quality of the cut. A poor choice of cutting conditions can easily overheatdamage
the specimen, producing an alteration of the microstructure. As a general rule, Generally, soft materials are cut with a hard bond
wheelblade and hard materials with a soft bond wheel.blade. Aluminum oxide abrasive wheelsblades are preferred for ferrous
metals and silicon carbide wheelsblades are preferred for nonferrous alloys. Abrasive cut-off wheelsblades are essential for
sectioning metals with hardnesseshardness above about 35 HRC.350 HV. Extremely hard metallic materials and ceramics may be
more effectively cut using diamond-impregnated cutting wheels.blades. Manufacturer’s instructions should be followed as to the
choice of wheel and speeds.
6.1.3Flame cutting completely alters blade. Table 1 lists the structure of the metal at the flame cut edge. If flame cutting
suggested cutoff blades for materials with various Vickers (HV) hardness values.
7.1.3 Ashear is necessary to remove the specimen, it should be cut sufficiently large so that it can be recut to a type of cutting
tool with which a material in the proper size by some other method that will not substan
...
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