ASTM E3-2011 5000 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 11Standard 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 number in parentheses

2、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 Department of Defense.1. Scope1.1 The primary objective of metallographic examinationsis to reveal the constit

3、uents 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 andpreparation of the speci

4、men 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 describe the vari

5、ations 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, 3rdEd., 1982; Petzow,

6、 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 standard to establ

7、ish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:A90/A90M Test Method for Weight Mass of Coating onIron and Steel Articles with Zinc or Zinc-Alloy Coatings2E7 Terminology Relating to Metallo

8、graphyE45 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 for Obtaining JK Inclusion Ratings UsingAut

9、omatic Image Analysis3E1245 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 Electrolytic Polishing of MetallographicSpecimensE1920 Guide f

10、or 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 metallographic mount generallymade from a two component castable plasti

11、c. 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 that requires both heat and pressure for curing.3.2.3 planar

12、 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 equipment that utilize specimen holders.3.2.4 rigid grinding disca non-fabric support surface,such as a composite of metal/cera

13、mic or metal/polymer1This guide is under the jurisdiction ofASTM Committee E04 on Metallographyand is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.Current edition approved May 1, 2011. Published June 2011. Originallyapproved in 1921. Last previous edition approved in 2007

14、 as 01(2007)1. DOI:10.1520/E0003-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last appr

15、oved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.charged with an abrasive (usually 6 to 15m diamond par-ticles), and used as the fine grinding operation in a metall

16、o-graphic 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 ofmetallographic examination.4.2 Many specifications contain a requirem

17、ent 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.4.3 Proper choice of specimen location and orientation willminim

18、ize 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 specimens for metallographicexamination is extremely important because, i

19、f 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 studied. With respect to purpose of study,metallographic examination ma

20、y 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 from a casting in the zones whereinmaximum segregation might be exp

21、ected 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 asclosely as possible to the fracture or to the initiation of th

22、efailure. 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 comparisonof structures and properties.5.1.3 Research StudiesThe nat

23、ure 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 to be examined mustbe decided.5.2.1 For a casting, a section cut p

24、erpendicular 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-tions may require specimens with surfaces prepared parallel tothe o

25、riginal 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 cross sections taken perpendicu-lar to the main axis of the mate

26、rial 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 ferrous material(see Test Method E1077),5.3.4 Depth of surface imperfections,5.3.

27、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 infor-mation:5.4.1 Inclusion content of steel (see Practices E45,

28、 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 locations of surfaces examined should always begiven in reporting r

29、esults 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 not more than about 12 to 25Symbol inDiagramSuggested Designati

30、onA Rolled surfaceB Direction of rollingC Rolled edgeD Planar sectionE Longitudinal section perpendicular to rolled surfaceF Transverse sectionG Radial longitudinal sectionH Tangential longitudinal sectionFIG. 1 Method of Designating Location of Area Shown inPhotomicrograph.E3112mm (0.5 to 1.0 in.)

31、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 Specimens that are, fragile, oddly shaped or too

32、 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 Specimens7.1 In cutting the metallographic specimen f

33、rom 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 be used on all materialswith hardnesses below a

34、pproximately 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 for fine grinding. This method of sectioningis normally faster than sawing. The choice of cut-o

35、ff 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. Generally, softmaterials are cut with a hard bond blade and har

36、d 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 about 350HV. Extremely hard metallic materials and ceramics

37、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.7.1.3 A shear is a type of cutting tool with which a materialin

38、 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 damage, which willhave to be removed in subsequent preparation st

39、eps.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 thoroughly canprevent cold mounting resins from adhering to the

40、 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, if possible. If etching is required, when studying theunderl

41、ying 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) or in dilute hydrochloric acid (HCl). The HNO3method requir

42、es 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 found in Test Method A90/A90M.NOTE 2Picral etchant produces l

43、ittle 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 two useful inhibitors.8.3 Oxidized or corroded surfaces may b

44、e 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, oroddly shaped specimens, fractures, or in instances where t

45、hespecimen 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 specimens into a pack held together by twoend pieces and two bolts

46、.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 specimen may be used in order to minimize theseepage of polishing materials and etchants. Use o

47、f 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 etching. Thin piecesof plastic, lead, or copper are typical materials that are used.Copper is espe

48、cially good for steel specimens since the usualetchants for steels will not attack the copper.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

49、 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 contamination and seepage,and prevent loss of friable or loose components. Impregnationis accomplished b