1、Designation: E1268 01 (Reapproved 2016)Standard Practice forAssessing the Degree of Banding or Orientation ofMicrostructures1This standard is issued under the fixed designation E1268; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONSegregation occurs during the dendritic solidification of metals and alloys and is aligned bysubsequent d
3、eformation. 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 examp
4、les 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 for d
5、etermining 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 a
6、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 stereo
7、logical 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 de
8、scribes 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 estimated
9、 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 me
10、asured 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 th
11、is 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:2A370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA572/A572M Specification for High-Strength Low
12、-AlloyColumbium-Vanadium Structural SteelA588/A588M 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 practice is u
13、nder the jurisdiction of ASTM Committee E04 on Metallog-raphy and is the direct responsibility of Subcommittee E04.14 on QuantitativeMetallography.Current edition approved Jan. 1, 2016. Published April 2016. Originallyapproved in 1988. Last previous edition approved in 2007 as E1268 01(2007).DOI: 10
14、.1520/E1268-01R162For 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.Copyright ASTM International, 100 Barr Harbo
15、r Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E140 Hardness Conversion Tables for Metals RelationshipAmong Brinell Hardness, Vickers Hardness, RockwellHardness, Superficial Hardness, Knoop Hardness, Sclero-scope Hardness, and Leeb HardnessE384 Test Method for Knoop and Vicker
16、s Hardness ofMaterialsE407 Practice for Microetching Metals and AlloysE562 Test Method for Determining Volume Fraction bySystematic Manual Point CountE883 Guide for ReflectedLight Photomicrography3. Terminology3.1 DefinitionsFor definitions of terms used in thispractice, see Terminology E7.3.2 Defin
17、itions of Terms Specific to This Standard:3.2.1 banded microstructureseparation, of one or morephases or constituents in a two-phase or multiphasemicrostructure, or of segregated regions in a single phase orconstituent microstructure, into distinct layers parallel to thedeformation axis due to elong
18、ation of microsegregation; otherfactors may also influence band formation, for example, the hotworking finishing temperature, the degree of hot- or cold-workreduction, or split transformations due to limited hardenabilityor insufficient quench rate.3.2.2 feature interceptionsthe number of particles
19、(orclusters of particles) of 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). F
20、orisolated particles in a matrix, 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
21、 elongation varies with the 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 2Mic
22、rostructural examples are presented 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:N= number of feature interceptions with test linesperpendicular t
23、o the deformation direction.N|= number of feature interceptions with test linesparallel to the deformation direction.M = magnification.Lt= true test line length in mm, that is, the test linelength divided by M.NL=NLtNL|=N|LtNOTE 1The test grid lines have been shown oriented perpendicular (A) to the
24、deformation axis 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.
25、1 Illustration of the Counting of Particle Interceptions (N) and Boundary Intersections (P) for an Oriented MicrostructureE1268 01 (2016)2P= number of feature boundary intersections withtest lines perpendicular to the deformation direc-tion.P|= number of feature boundary intersections withtest lines
26、 parallel to the deformation direction.PL=PLt2NLPL|=P|Lt2NL |n = number of measurement fields or number ofmicroindentation impressions.NL= (NLnNL|= (NL |nPL= (PLn2NLPL|= (PL |n2NL |X= mean values (NL, NL|, PL, PL|)s = estimate of standard deviation ().t = a multiplier related to the number of fields
27、examined and used in conjunction with the stan-dard deviation of the measurements to determinethe 95 % CI.95 % CI = 95 % confidence interval.95 % CI =6ts=n% RA = % relative accuracy.% RA =95% CIX3100SB= mean center-to-center spacing of the bands.SB=1NL.VV= volume fraction of the banded phase (consti
28、tu-ent).= mean edge-to-edge spacing of the bands, meanfree path (distance).=12VVNLAI = anisotropy index.AI =NLNL|5PLPL|12= degree of orientation of partially oriented linearstructure elements on the two-dimensional plane-of-polish.12=NL 2NL |NL10.571 NL |12=PL2PL |PL10.571 PL|4. Summary of Practice4
29、.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 measure the numberof bands per unit length, the inter-band or interparticle spacingand th
30、e 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.FIG. 2 Qualitative Classification Scheme for Oriented or Banded MicrostructuresE1268 01 (2
31、016)35. Significance 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 p
32、hase or multiphase 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 Micro
33、structural 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 mat
34、erial. The 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 m
35、easuring individual 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 pur
36、chaser and 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 b
37、est observed using low magnifications, forexample, 50 to 200.6.2 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 t
38、he test lines 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 tab
39、let anda 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,
40、or other 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
41、.7. Sampling 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 s
42、ection, the 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 agreem
43、ents.7.2 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 o
44、r sheet) 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 con
45、trol purposes. 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 nu
46、mber and 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
47、least 10 mm (0.4 in.). If theproduct form is too large to permit preparation of full crosssections, the samples prepared at the desired locations shouldhave 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 P
48、reparation8.1 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.3Lpine, M., “Imag
49、e Convolutions and their Application to QuantitativeMetallography,” Microstructural Science, Vol. 17, Image Analysis andMetallography, ASM 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 Park, OH, 1990, pp. 1321.E1268 01 (2016)48.2 Mou
