ASTM E3-2011(2017) 6875 Standard Guide for Preparation of Metallographic Specimens《金相试样制备标准指南》.pdf

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1、Designation: E3 11(Reapproved 2017)Standard Guide forPreparation of Metallographic Specimens1This standard is issued under the fixed designation E3; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A numbe

2、r in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 The primary objective of metallographic examinationsis

3、 to reveal 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 andpr

4、eparation 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

5、 not 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,

6、 3rdEd., 1982; Petzow, G., Metallographic Etching, ASM, 1978; andVanderVoort, G., Metallography: Principles and Practice, McGraw Hill,NY, 2nd Ed., 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 thi

7、s standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.3 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principl

8、es for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:A90/A90M Test Method for Weight Mass of Coating onIron and Steel Articles with Zinc or Zinc-Alloy

9、Coatings2E7 Terminology Relating to MetallographyE45 Test Methods for Determining the Inclusion Content ofSteelE768 Guide for Preparing and Evaluating Specimens forAutomatic Inclusion Assessment of SteelE1077 Test Methods for Estimating the Depth of Decarbur-ization of Steel SpecimensE1122 Practice

10、for Obtaining JK Inclusion Ratings UsingAutomatic Image Analysis (Withdrawn 2006)3E1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic ImageAnalysisE1268 Practice for Assessing the Degree of Banding orOrientation of MicrostructuresE1558 Guide for El

11、ectrolytic Polishing of MetallographicSpecimensE1920 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 Terms Specific to This Standard:3.2.1 castable mounta metallograp

12、hic 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 cure.3.2.2 compression mounta metallographic mount madeusing plastic

13、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 same1This guide is under the jurisdiction ofASTM Committee E04 on Metallographyand is the direct responsibility of Subcommittee E04.01 on S

14、pecimen Preparation.Current edition approved June 1, 2017. Published June 2017. Originallyapproved in 1921. Last previous edition approved in 2011 as E3 1111. DOI:10.1520/E0003-11R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.

15、org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-

16、2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technica

17、l Barriers to Trade (TBT) Committee.1plane of polish. It is unique to semi or fully automaticpreparation equipment 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 diamo

18、ndparticles), and used as the fine grinding operation in a metal-lographic preparation procedure.4. Significance 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 ofmeta

19、llographic examination.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 research and development

20、.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 of test specimen

21、s 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 specimens to be studie

22、d. 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 could be taken fr

23、om 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 specimens should be taken

24、 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 sound area for a com

25、parisonof 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 type of section t

26、o 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. Special investiga-ti

27、ons 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 Transverse sections or

28、 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 thesection,5.3.3 Decarburization at the surface of a ferrous material(s

29、ee Test Method E1077),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 E1920.5.4 Longitudinal sections taken parallel to the main axis ofthe material are often used for revealing the following in

30、for-mation:5.4.1 Inclusion content of steel (see Practices E45, E768,E1122, and E1245),5.4.2 Degree of plastic deformation, as shown by graindistortion,5.4.3 Presence or absence of banding in the structure (seePractice E1268), and5.4.4 The microstructure attained with any heat treatment.5.5 The loca

31、tions 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 examination are generally

32、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 difficult to pre-pare.6.1.2

33、Specimens that are, fragile, oddly shaped or too smallto be handled readily during polishing should be mounted toensure a surface satisfactory for microscopical study. Thereare, based on technique used, three fundamental methods ofmounting specimens (see Section 9).7. Cutting of Metallographic Speci

34、mens7.1 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 lubrication,is easy, fast, and relatively cool. It can

35、 be used on all materialswith hardnesses below approximately 350 HV. It does produceE3 11(2017)2a 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 for fine grinding. This method of s

36、ectioningis 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 alteration of the microstructure. Gen

37、erally, 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 sectioning metals with hardness above

38、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 various Vickers (HV) hardness values.7.1

39、.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 operations produce some depth of damag

40、e, 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 organic solvent. Failure to clean tho

41、roughly 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 should be removed beforepolishing,

42、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 1.42), in dilute sulfuric acid(H2SO4)

43、 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 minimized. Moreinformation may be f

44、ound in Test Method A90/A90M.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(polethylinepolyamine) or SbCl3are t

45、wo 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 usually performed on small, fragile,

46、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 by bindingor clamping several specim

47、ens 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.Symbol inDiagramSuggested DesignationA Rolled surfaceB Direction of rollingC Rolled edgeD Planar sectionE

48、Longitudinal section perpendicular to rolled surfaceF Transverse sectionG Radial longitudinal sectionH Tangential longitudinal sectionFIG. 1 Method of Designating Location of Area Shown in Photo-micrograph.TABLE 1 Cutoff Blade SelectionHardnessHVMaterials Abrasive BondBondHardnessup to 300 non-ferro

49、us (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 can cause dermatitis.Manufacturers recommendations for mixing and curing mustbe followed to obtain best results.9.5 Mounting Porous Specimen:9.5.1 Porous or intricate specimens may be vacuum impreg-nated in order to fill voids, prevent