ASTM E1268-2001(2007) Standard Practice for Assessing the Degree of Banding or Orientation of Microstructures《评定显微结构带状物等级或取向的标准实施规范》.pdf

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1、Designation: E 1268 01 (Reapproved 2007)Standard Practice forAssessing the Degree of Banding or Orientation ofMicrostructures1This standard is issued under the fixed designation E 1268; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio

2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONSegregation occurs during the dendritic solidification of metals and alloys and is aligned bysubsequen

3、t deformation. Solid-state transformations may be influenced by the resulting microsegre-gation pattern leading to development of a layered or banded microstructure. The most commonexample of banding is the layered ferrite-pearlite structure of wrought low-carbon and low-carbonalloy steels. Other ex

4、amples of banding include carbide banding in hypereutectoid tool steels andmartensite banding in heat-treated alloy steels. This practice covers procedures to describe theappearance of banded structures, procedures for characterizing the extent of banding, and amicroindentation hardness procedure fo

5、r determining the difference in hardness between bands in heattreated specimens. The stereological methods may also be used to characterize non-bandedmicrostructures with second phase constituents oriented (elongated) in varying degrees in thedeformation direction.1. Scope1.1 This practice describes

6、 a procedure to qualitativelydescribe the nature of banded or oriented microstructures basedon the morphological appearance of the microstructure.1.2 This practice describes stereological procedures forquantitative measurement of the degree of microstructuralbanding or orientation.NOTE 1Although ste

7、reological measurement methods are used toassess the degree of banding or alignment, the measurements are onlymade on planes parallel to the deformation direction (that is, a longitudinalplane) and the three-dimensional characteristics of the banding or align-ment are not evaluated.1.3 This practice

8、 describes a microindentation hardness testprocedure for assessing the magnitude of the hardness differ-ences present in banded heat-treated steels. For fully marten-sitic carbon and alloy steels (0.100.65 %C), in the as-quenched condition, the carbon content of the matrix andsegregate may be estima

9、ted from the microindentation hard-ness values.1.4 This standard does not cover chemical analytical meth-ods for evaluating banded structures.1.5 This practice deals only with the recommended testmethods and nothing in it should be construed as defining orestablishing limits of acceptability.1.6 The

10、 measured values are stated in SI units, which areregarded as standard. Equivalent inch-pound values, whenlisted, are in parentheses and may be approximate.1.7 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of

11、 this standard 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:2A 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA 572/A 572M Specification for High-Streng

12、th Low-AlloyColumbium-Vanadium Structural SteelA 588/A 588M Specification for High-Strength Low-AlloyStructural Steel, up to 50 ksi 345 MPa Minimum YieldPoint, with Atmospheric Corrosion ResistanceE3 Guide for Preparation of Metallographic SpecimensE7 Terminology Relating to Metallography1This pract

13、ice is under the jurisdiction of ASTM Committee E04 on Metallog-raphy and is the direct responsibility of Subcommittee E04.14 on QuantitativeMetallography.Current edition approved May 1, 2007. Published May 2007 . Originallyapproved in 1988. Last previous edition approved in 2001 as E 1268 01.2For r

14、eferenced 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,

15、West Conshohocken, PA 19428-2959, United States.E 140 Hardness Conversion Tables for Metals RelationshipAmong Brinell Hardness, Vickers Hardness, RockwellHardness, Superficial Hardness, Knoop Hardness, andScleroscope HardnessE 384 Test Method for Microindentation Hardness of Ma-terialsE 407 Practice

16、 for Microetching Metals and AlloysE 562 Test Method for Determining Volume Fraction bySystematic Manual Point CountE 883 Guide for ReflectedLight Photomicrography3. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, see Terminology E7.3.2 Definitions of Terms Specific to Thi

17、s Standard:3.2.1 banded microstructureseparation, of one or morephases or constituents in a two-phase or multiphase microstruc-ture, or of segregated regions in a single phase or constituentmicrostructure, into distinct layers parallel to the deformationaxis due to elongation of microsegregation; ot

18、her factors mayalso influence band formation, for example, the hot workingfinishing temperature, the degree of hot- or cold-work reduc-tion, or split transformations due to limited hardenability orinsufficient quench rate.3.2.2 feature interceptionsthe number of particles (orclusters of particles) o

19、f a phase or constituent of interest thatare crossed by the lines of a test grid. (see Fig. 1).3.2.3 feature intersectionsthe number of boundaries be-tween the matrix phase and the phase or constituent of interestthat are crossed by the lines of a test grid (see Fig. 1). Forisolated particles in a m

20、atrix, the number of feature intersec-tions will equal twice the number of feature interceptions.3.2.4 oriented constituentsone or more second-phases(constituents) elongated in a non-banded (that is, randomdistribution) manner parallel to the deformation axis; thedegree of elongation varies with the

21、 size and deformability ofthe phase or constituent and the degree of hot- or cold-workreduction.3.2.5 stereological methodsprocedures used to character-ize three-dimensional microstructural features based on mea-surements made on two-dimensional sectioning planes.NOTE 2Microstructural examples are p

22、resented in Annex A1 toillustrate the use of terminology for providing a qualitative description ofthe nature and extent of the banding or orientation. Fig. 2 describes theclassification approach.3.3 Symbols:NOTE 1The test grid lines have been shown oriented perpendicular (A) to the deformation axis

23、 and parallel (B) to the deformation axis. The countsfor N, N|, P, and P|are shown for counts made from top to bottom (A) or from left to right (B).NOTE 2T indicates a tangent hit and E indicates that the grid line ended within the particle; both situations are handled as shown.FIG. 1 Illustration o

24、f the Counting of Particle Interceptions (N) and Boundary Intersections (P) for an Oriented MicrostructureE 1268 01 (2007)2N= number of feature interceptions with test linesperpendicular to the deformation direction.N|= number of feature interceptions with test linesparallel to the deformation direc

25、tion.M = magnification.Lt= true test line length in mm, that is, the test linelength divided by M.NL=NLtNL|=N|LtP= number of feature boundary intersections withtest lines perpendicular to the deformation di-rection.P|= number of feature boundary intersections withtest lines parallel to the deformati

26、on direction.PL=PLt 2NLPL|=P|Lt 2NL |n = number of measurement fields or number ofmicroindentation impressions.NL =(NLnNL|=(NL |nPL=(PLn 2NLPL|=(PL |n 2NL |X=mean values ( NL, NL|, PL , PL|)s = estimate of standard deviation (s).t = a multiplier related to the number of fieldsexamined and used in co

27、njunction with thestandard deviation of the measurements to de-termine the 95 % CI.95 % CI = 95 % confidence interval.95 % CI =6ts=n% RA = % relative accuracy.% RA =95 % CIX3 100SB= mean center-to-center spacing of the bands.SB=1NL.VV= volume fraction of the banded phase (constitu-ent).l= mean edge-

28、to-edge spacing of the bands, meanfree path (distance).l=1 2 VVNLAI = anisotropy index.AI =NLNL|5PLPL|V12= degree of orientation of partially oriented linearstructure elements on the two-dimensionalplane-of-polish.V12=NL2 NL |NL1 0.571 NL |FIG. 2 Qualitative Classification Scheme for Oriented or Ban

29、ded MicrostructuresE 1268 01 (2007)3V12=PL2 PL |PL1 0.571 PL|4. Summary of Practice4.1 The degree of microstructural banding or orientation isdescribed qualitatively using metallographic specimensaligned parallel to the deformation direction of the product.4.2 Stereological methods are used to measu

30、re the numberof bands per unit length, the inter-band or interparticle spacingand the degree of anisotropy or orientation.4.3 Microindentation hardness testing is used to determinethe hardness of each type band present in hardened specimensand the difference in hardness between the band types.5. Sig

31、nificance and Use5.1 This practice is used to assess the nature and extent ofbanding or orientation of microstructures of metals and othermaterials where deformation and processing produce a bandedor oriented condition.5.2 Banded or oriented microstructures can arise in singlephase, two phase or mul

32、tiphase metals and materials. Theappearance of the orientation or banding is influenced byprocessing factors such as the solidification rate, the extent ofsegregation, the degree of hot or cold working, the nature of thedeformation process used, the heat treatments, and so forth.5.3 Microstructural

33、banding or orientation influence theuniformity of mechanical properties determined in various testdirections with respect to the deformation direction.5.4 The stereological methods can be applied to measure thenature and extent of microstructural banding or orientation forany metal or material. The

34、microindentation hardness testprocedure should only be used to determine the difference inhardness in banded heat-treated metals, chiefly steels.5.5 Isolated segregation may also be present in an otherwisereasonably homogeneous microstructure. Stereological meth-ods are not suitable for measuring in

35、dividual features, insteaduse standard measurement procedures to define the featuresize. The microindentation hardness method may be used forsuch structures.5.6 Results from these test methods may be used to qualifymaterial for shipment in accordance with guidelines agreedupon between purchaser and

36、manufacturer, for comparison ofdifferent manufacturing processes or process variations, or toprovide data for structure-property-behavior studies.6. Apparatus6.1 A metallurgical (reflected-light) microscope is used toexamine the microstructure of test specimens. Banding ororientation is best observe

37、d using low magnifications, forexample, 503 to 2003.6.2 Stereological measurements are made by superimposinga test grid (consisting of a number of closely spaced parallellines of known length) on the projected image of the micro-structure or on a photomicrograph. Measurements are madewith the test l

38、ines parallel and perpendicular to the deformationdirection. The total length of the grid lines should be at least500 mm.6.3 These stereological measurements may be made using asemiautomatic tracing type image analyzer. The test grid isplaced over the image projected onto the digitizing tablet anda

39、cursor is used for counting.6.4 For certain microstructures where the contrast betweenthe banded or oriented constituents is adequate, an automaticimage analyzer may be used for counting, where the TV scanlines for a live image, or image convolutions3, electronically-generated test grids4, or other

40、methods, for a digitized image,are used rather than the grid lines of the plastic overlay orreticle.6.5 A microindentation hardness tester is used to determinethe hardness of each type of band in heat-treated steels or othermetals. The Knoop indenter is particularly well suited for thiswork.7. Sampl

41、ing and Test Specimens7.1 In general, specimens should be taken from the finalproduct form after all processing steps have been performed,particularly those that would influence the nature and extent ofbanding. Because the degree of banding or orientation mayvary through the product cross section, t

42、he test plane shouldsample the entire cross section. If the section size is too largeto permit full cross sectioning, samples should be taken atstandard locations, for example, subsurface, mid-radius (orquarter-point), and center, or at specific locations based uponproducer-purchaser agreements.7.2

43、The degree of banding or orientation present is deter-mined using longitudinal test specimens, that is, specimenswhere the plane of polish is parallel to the deformationdirection. For plate or sheet products, a planar oriented (that is,polished surface parallel to the surface of the plate or sheet)

44、testspecimen, at subsurface, mid-thickness, or center locations,may also be prepared and tested depending on the nature of theproduct application.7.3 Banding or orientation may also be assessed on inter-mediate product forms, such as billets or bars, for materialqualification or quality control purp

45、oses. These test results,however, may not correlate directly with test results on finalproduct forms. Test specimens should be prepared as describedin 7.1 and 7.2 but with the added requirement of choosing testlocations with respect to ingot or continuously cast slab/strandlocations. The number and

46、location of such test specimensshould be defined by producer-purchaser agreement.7.4 Individual metallographic test specimens should have apolished surface area covering the entire cross section ifpossible. The length of full cross-section samples, in thedeformation direction, should be at least 10

47、mm (0.4 in.). If theproduct form is too large to permit preparation of full crosssections, the samples prepared at the desired locations should3Lpine, M., “Image Convolutions and their Application to QuantitativeMetallography,” Microstructural Science, Vol. 17, Image Analysis and Metallogra-phy, ASM

48、 International, Metals Park, OH, 1989, pp. 103114.4Fowler, D.B., “A Method for Evaluating Plasma Spray Coating PorosityContent Using Stereological Data Collected by Automatic Image Analysis,”Microstructural Science, Vol. 18, Computer-Aided Microscopy and Metallography,ASM International, Materials Pa

49、rk, OH, 1990, pp. 1321.E 1268 01 (2007)4have a minimum polished surface area of 100 mm2(0.16 in.2)with the sample length in the longitudinal direction at least 10mm (0.4 in.).8. Specimen Preparation8.1 Metallographic specimen preparation should be per-formed in accordance with the guidelines and recommendedpractices given in Methods E3. The preparation proceduremust reveal the microstructure without excessive influencefrom preparation-induced deformation or smearing.8.2 Mounting of specim