1、Designation:E301(Reapproved 2007)Standard Guide forPreparation of Metallographic Specimens1This standard is issued under the fixed designation E 3; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A number
2、 in parentheses indicates the year of last reapproval. A superscriptepsilon (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. Scope1.1 The primary objective of metallographic examinationsis to r
3、eveal the constituents and structure of metals and theiralloys by means of a light optical or scanning electronmicroscope. In special cases, the objective of the examinationmay require the development of less detail than in other casesbut, under nearly all conditions, the proper selection andprepara
4、tion of the specimen is of major importance. Because ofthe diversity in available equipment and the wide variety ofproblems encountered, the following text presents for theguidance of the metallographer only those practices whichexperience has shown are generally satisfactory; it cannot anddoes not
5、describe the variations in technique required to solveindividual specimen preparation problems.NOTE 1For a more extensive description of various metallographictechniques, refer to Samuels, L. E., Metallographic Polishing by Mechani-cal Methods, American Society for Metals (ASM) Metals Park, OH, 3rdE
6、d., 1982; Petzow, G., Metallographic Etching, ASM, 1978; and Vander-Voort, G., Metallography: Principles and Practice, McGraw Hill, NY, 2ndEd., 1999.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this s
7、tandard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:A 90/A 90M Test Method for Weight Mass of Coating onIron and Steel Articles with Zinc or Zinc-Alloy CoatingsE7 Terminology R
8、elating to MetallographyE45 Test Methods for Determining the Inclusion Contentof SteelE 340 Test Method for Macroetching Metals and AlloysE 407 Practice for Microetching Metals and AlloysE 768 Guide for Preparing and Evaluating Specimens forAutomatic Inclusion Assessment of SteelE 1077 Test Methods
9、for Estimating the Depth of Decar-burization of Steel SpecimensE 1122 Practice for Obtaining JK Inclusion Ratings UsingAutomatic Image Analysis2E 1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic ImageAnalysisE 1268 Practice for Assessing the Degr
10、ee of Banding orOrientation of MicrostructuresE 1558 Guide for Electrolytic Polishing of MetallographicSpecimensE 1920 Guide for Metallographic Preparation of ThermalSprayed Coatings3. Terminology3.1 Definitions:3.1.1 For definitions used in this practice, refer to Termi-nology E7.3.2 Definitions of
11、 Terms Specific to This Standard:3.2.1 castable mounta metallographic mount generallymade from a two component castable plastic. One componentis the resin and the other hardener. Both components can heliquid or one liquid and a powder. Castable mounts generallydo not require heat and pressure to cur
12、e.3.2.2 compression mounta metallographic mount madeusing plastic that requires both heat and pressure for curing.3.2.3 planar grindingis the first grinding step in a prepa-ration procedure used to bring all specimens into the sameplane of polish. It is unique to semi or fully automaticpreparation e
13、quipment that utilize specimen holders.3.2.4 rigid grinding disca non-fabric support surface,such as a composite of metal/ceramic or metal/polymercharged with an abrasive (usually 6 to 15m diamond par-ticles), and used as the fine grinding operation in a metallo-graphic preparation procedure.4. Sign
14、ificance and Use4.1 Microstructures have a strong influence on the proper-ties and successful application of metals and alloys. Determi-nation and control of microstructure requires the use ofmetallographic examination.1This guide is under the jurisdiction ofASTM Committee E04 on Metallographyand is
15、 the direct responsibility of Subcommittee E04.01 on Specimen Preparation.Current edition approved July 1, 2007. Published September 2007. Originallyapproved in 1921. Last previous edition approved in 2001 as E301.2Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
16、shohocken, PA 19428-2959, United States.4.2 Many specifications contain a requirement regardingmicrostructure; hence, a major use for metallographic exami-nation is inspection to ensure that the requirement is met. Othermajor uses for metallographic examination are in failureanalysis, and in researc
17、h and development.4.3 Proper choice of specimen location and orientation willminimize the number of specimens required and simplify theirinterpretation. It is easy to take too few specimens for study,but it is seldom that too many are studied.5. Selection of Metallographic Specimens5.1 The selection
18、 of test specimens for metallographicexamination is extremely important because, if their interpre-tation is to be of value, the specimens must be representative ofthe material that is being studied. The intent or purpose of themetallographic examination will usually dictate the location ofthe speci
19、mens to be studied. With respect to purpose of study,metallographic examination may be divided into three classi-fications:5.1.1 General Studies or Routine WorkSpecimens shouldbe chosen from locations most likely to reveal the maximumvariations within the material under study. For example,specimens
20、could be taken from a casting in the zones whereinmaximum segregation might be expected to occur as well asspecimens from sections where segregation could be at aminimum. In the examination of strip or wire, test specimenscould be taken from each end of the coils.5.1.2 Study of FailuresTest specimen
21、s should be taken asclosely as possible to the fracture or to the initiation of thefailure. Before taking the metallographic specimens, study ofthe 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 sou
22、nd area for a comparisonof structures and properties.5.1.3 Research StudiesThe nature of the study will dictatespecimen location, orientation, etc. Sampling will usually bemore extensive than in routine examinations.5.2 Having established the location of the metallographicsamples to be studied, the
23、type of section to be examined mustbe decided.5.2.1 For a casting, a section cut perpendicular to thesurface will show the variations in structure from the outside tothe interior of the casting.5.2.2 In hot-worked or cold-worked metals, both transverseand longitudinal sections should be studied. Spe
24、cial investiga-tions may require specimens with surfaces prepared parallel tothe original surface of the product.5.2.3 In the case of wire and small rounds, a longitudinalsection through the center of the specimen proves advanta-geous when studied in conjunction with the transverse section.5.3 Trans
25、verse sections or cross sections taken perpendicu-lar to the main axis of the material are often used for revealingthe following information:5.3.1 Variations in structure from center to surface,5.3.2 Distribution of nonmetallic impurities across the sec-tion,5.3.3 Decarburization at the surface of a
26、 ferrous material(see Test Method E 1077),5.3.4 Depth of surface imperfections,5.3.5 Depth of corrosion,5.3.6 Thickness of protective coatings, and5.3.7 Structure of protective coating. See Guide E 1920.5.4 Longitudinal sections taken parallel to the main axis ofthe material are often used for revea
27、ling the following infor-mation:5.4.1 Inclusion content of steel (see Practices E45, E 768,E 1122, and E 1245),5.4.2 Degree of plastic deformation, as shown by graindistortion,5.4.3 Presence or absence of banding in the structure (seePractice E 1268), and5.4.4 The microstructure attained with any he
28、at treatment.5.5 The locations of surfaces examined should always begiven in reporting results and in any illustrative micrographs.Asuitable method of indicating surface locations is shown in Fig.1.6. Size of Metallographic Specimens6.1 For convenience, specimens to be polished for metallo-graphic e
29、xamination are generally not more than about 12 to 25mm (0.5 to 1.0 in.) square, or approximately 12 to 25 mm indiameter if the material is cylindrical. The height of thespecimen should be no greater than necessary for convenienthandling during polishing.6.1.1 Larger specimens are generally more dif
30、ficult to pre-pare.6.1.2 Specimens that are, fragile, oddly shaped or too smallto be handled readily during polishing should be mounted toensure a surface satisfactory for microscopical study. ThereSymbol inDiagramSuggested DesignationA Rolled surfaceB Direction of rollingC Rolled edgeD Planar secti
31、onE Longitudinal section perpendicular to rolled surfaceF Transverse sectionG Radial longitudinal sectionH Tangential longitudinal sectionFIG. 1 Method of Designating Location of Area Shown inPhotomicrograph.E301(2007)2are, based on technique used, three fundamental methods ofmounting specimens (see
32、 Section 9).7. Cutting of Metallographic Specimens7.1 In cutting the metallographic specimen from the mainbody of the material, care must be exercised to minimizealtering the structure of the metal. Three common types ofsectioning are as follows:7.1.1 Sawing, whether by hand or machine with lubricat
33、ion,is easy, fast, and relatively cool. It can be used on all materialswith hardnesses below approximately 350 HV. It does producea rough surface containing extensive plastic flow that must beremoved in subsequent preparation.7.1.2 An abrasive cut-off blade will produce a smoothsurface often ready f
34、or fine grinding. This method of sectioningis normally faster than sawing. The choice of cut-off blade,lubricant, cooling conditions, and the grade and hardness ofmetal being cut will influence the quality of the cut. A poorchoice of cutting conditions can easily damage the specimen,producing an alt
35、eration of the microstructure. Generally, softmaterials are cut with a hard bond blade and hard materialswith a soft bond blade. Aluminum oxide abrasive blades arepreferred for ferrous metals and silicon carbide blades arepreferred for nonferrous alloys. Abrasive cut-off blades areessential for sect
36、ioning metals with hardness above about 350HV. Extremely hard metallic materials and ceramics may bemore effectively cut using diamond-impregnated cuttingblades. Manufacturers instructions should be followed as tothe choice of blade. Table 1 lists the suggested cutoff blades formaterials with variou
37、s Vickers (HV) hardness values.7.1.3 A shear is a type of cutting tool with which a materialin the form of wire, sheet, plate or rod is cut between twoopposing blades.7.2 Other methods of sectioning are permitted provided theydo not alter the microstructure at the plane of polishing. Allcutting oper
38、ations produce some depth of damage, which willhave to be removed in subsequent preparation steps.8. Cleanliness8.1 Cleanliness (see Appendix X1) during specimen prepa-ration is essential. All greases, oils, coolants and residue fromcutoff blades on the specimen should be removed by somesuitable org
39、anic solvent. Failure to clean thoroughly canprevent cold mounting resins from adhering to the specimensurface. Ultrasonic cleaning may be effective in removing thelast traces of residues on a specimen surface.8.2 Any coating metal that will interfere with the subse-quent etching of the base metal s
40、hould be removed beforepolishing, if possible. If etching is required, when studying theunderlying steel in a galvanized specimen, the zinc coatingshould be removed before mounting to prevent galvanic effectsduring etching. The coating can be removed by dissolving incold nitric acid (HNO3, sp gr 1.4
41、2), in dilute sulfuric acid(H2SO4) or in dilute hydrochloric acid (HCl). The HNO3method requires care to prevent overheating, since largesamples will generate considerable heat. By placing the clean-ing container in cold water during the stripping of the zinc,attack on the underlying steel will be m
42、inimized. Moreinformation may be found in Test Method A 90/A 90M.NOTE 2Picral etchant produces little or no galvanic etching effectswhen used on galvanized steel.NOTE 3The addition of an inhibitor during the stripping of Zn fromgalvanized coatings will minimize the attack of the steel substrate. NEP
43、(polethylinepolyamine) or SbCl3are two useful inhibitors.8.3 Oxidized or corroded surfaces may be cleaned asdescribed in Appendix X1.9. Mounting of Specimens9.1 There are many instances where it will be advantageousto mount the specimen prior to grinding and polishing. Mount-ing of the specimen is u
44、sually performed on small, fragile, oroddly shaped specimens, fractures, or in instances where thespecimen edges are to be examined.9.2 Specimens may be either mechanically mounted,mounted in plastic, or a combination of the two.9.3 Mechanical Mounting:9.3.1 Strip and sheet specimens may be mounted
45、by bindingor clamping several specimens into a pack held together by twoend pieces and two bolts.9.3.2 The specimens should be tightly bound together toprevent absorption and subsequent exudation of polishingmaterials or etchants.9.3.3 The use of filler sheets of a softer material alternatedwith the
46、 specimen may be used in order to minimize theseepage of polishing materials and etchants. Use of fillermaterial is especially advantageous if the specimens have ahigh degree of surface irregularities.9.3.4 Filler material must be chosen so as not to reactelectrolytically with the specimen during et
47、ching. Thin piecesof plastic, lead, or copper are typical materials that are used.Copper is especially good for steel specimens since the usualetchants for steels will not attack the copper.9.3.5 Alternatively, the specimens may be coated with alayer of epoxy resin before being placed in the clamp i
48、n orderto minimize the absorption of polishing materials or etchants.9.3.6 The clamp material should be similar in compositionto the specimen to avoid galvanic effects that would inhibitetching. The specimen will not etch if the clamp material ismore readily attacked by the etchant.9.3.7 The clamp s
49、hould preferably be of similar hardness asthe specimens to minimize the rounding of the edges of thespecimens during grinding and polishing.TABLE 1 Cutoff Blade SelectionHardness HV Materials Abrasive Bond Bond Hardnessup to 300 non-ferrous (Al, Cu) SiC P or R hardup to 400 non-ferrous (Ti) SiC P or R med. hardup to 400 soft ferrous Al2O3P or R hardup to 500 medium soft ferrous Al2O3P or R med. hardup to 600 medium hard ferrous Al2O3P or R mediumup to 700 hard ferrous Al2O3P or Rthe choice is a matter of convenience and cost. Handlingcastable resins requires care. They all c
