NORMA ASTM E 3 – 95 An American National Standard

Designation: E 3 – 95 An American National Standard

Standard Practice for

Preparation of Metallographic Specimens1

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. 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

1.1 The primary objective of metallographic examinations

is to reveal the constituents and structure of metals and their

alloys by means of the light 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 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 Vander-

Voort, G., Metallography: Principles and Practice, McGraw Hill, NY,

1984.

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:

E 7 Terminology Relating to Metallography2

E 45 Practice for Determining the Inclusion Content of

Steel2

E 340 Test Method for Macroetching Metals and Alloys2

E 407 Test Methods for Microetching Metals and Alloys2

E 1077 Test Method for Estimating the Depth of Decarburization

of Steel Specimens2

E 1268 Practice for Assessing the Degree of Banding or

Orientation of Microstructures2

E 1558 Guide to Electrolytic Polishing of Metallographic

Specimens2

3. Significance and Use

3.1 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.

3.2 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.

3.3 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.

4. Selection of Metallographic Specimens

4.1 The selection of test specimens for metallographic

examination is extremely important because, if their interpretation

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:

4.1.1 General Studies or Routine Work—Specimens from

locations that are most likely to reveal the maximum variations

within the material under study should be chosen. For example,

specimens should be taken from a casting in the zones wherein

maximum segregation might be expected to occur as well as

specimens from sections where segregation should be at a

minimum. In the examination of strip or wire, test specimens

should be taken from each end of the coils.

4.1.2 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 should

be taken in many cases from a sound area for a comparison of

structures and properties.

4.1.3 Research Studies—The nature of the study will dictate

specimen location, orientation, etc. Sampling will usually be

more extensive than in routine examinations.

4.2 Having established the location of the metallographic

samples to be studied, the type of section to be examined must

1 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.

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