ASTM E82 E82M-2014 7095 Standard Test Method for Determining the Orientation of a Metal Crystal《测定金属晶体取向的标准试验方法》.pdf

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1、Designation: E82/E82M 14Standard Test Method forDetermining the Orientation of a Metal Crystal1This standard is issued under the fixed designation E82/E82M; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.

2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the back-reflection Laue proce-dure for determining the orientation of a metal crystal. Theback-reflection L

3、aue method for determining crystal orienta-tion may be applied to macrograins and micrograins dependingon the beam size within polycrystalline aggregates, as well asto single crystals of any size. This test method is described withreference to cubic crystals and other structures such as:hexagonal, t

4、etragonal, or orthorhombic crystals.1.2 Most natural crystals have well developed externalfaces, and the orientation of such crystals can usually bedetermined from inspection. The orientation of a crystal havingpoorly developed faces or no faces at all (for example, a metalcrystal prepared in the la

5、boratory) shall be determined by moreelaborate methods. The most convenient and accurate of theseinvolves the use of X-ray diffraction. The “orientation of ametal crystal” is known when the positions in space of thecrystallographic axes of the unit cell have been located withreference to the surface

6、 geometry of the crystal specimen. Thisrelation between unit cell position and surface geometry ismost conveniently expressed by stereographic or gnomonicprojection.1.3 UnitsThe values stated in either SI units or inch-pound units are to be regarded separately as standard. Thevalues stated in each s

7、ystem may not be exact equivalents;therefore, each system shall be used independently of the other.Combining values from the two systems may result in non-conformance with the standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is the

8、responsibility of the user of 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:2E3 Guide for Preparation of Metallographic Specimens3. Summary of Test Method3.1 The ar

9、rangement of the apparatus is similar to that of thetransmission Laue method for crystal structure determination3,4except that the detector is located between the X-ray sourceand the specimen or beside the X-ray source in the case of sidereflection geometry. The incident beam of white X-radiationpas

10、ses through a pinhole aperture, strikes the crystal, and isthen diffracted back to the detector. White spots, whichrepresent X-ray beams “diffracted” by the atomic planes withinthe crystalline specimen, appear on the digital picture collectedby the detector. The indexation of the spots and their pos

11、itionsin space are calculated by simulation of the Laue patternsuperimposed onto the digital image collected by the detector.Older techniques based on film technology can also be used toindex the spots and to calculate the orientation of the crystal.4. Significance and Use4.1 The physical properties

12、 of metals and other materials areoften anisotropic (for example: Youngs modulus will typicallyvary in different crystallographic directions). As such, it isoften desirable or necessary to determine the orientation of asingle crystal to ascertain the relation of any pertinent physicalproperties with

13、 respect to different directions in the material.4.2 This test method can be used commercially as a qualitycontrol test in production situations in which a desiredorientation, within prescribed limits, is required.4.3 With the use of an adjustable, fixed holder that can laterbe mounted on a saw, lat

14、he, or other machine, a single crystal1This test method is under the jurisdiction of ASTM Committee E04 onMetallography and is the direct responsibility of Subcommittee E04.11 on X-Rayand Electron Metallography.Current edition approved May 1, 2014. Published August 2014. Originallyapproved in 1949.

15、Last previous edition approved in 2009 as E8209. DOI:10.1520/E0082-14.2For 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

16、 website.3Cullity, B. D., Elements of X-ray Diffraction, second edition, Addison-Wesley,Reading, MA, 1978.4Barrett, C. S. and Massalski, T. B., The Structure of Metals, 3rd edition,McGraw-Hill Inc., New York, 1966, pp. 211227.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con

17、shohocken, PA 19428-2959. United States1material can be moved to a preferred orientation and subse-quently sectioned, ground, or processed otherwise.4.4 If the grains in a polycrystalline material are largeenough, this test method can also be used to determine theirorientations and differences in or

18、ientation can be documentedor mapped or both.5. Apparatus5.1 X-Ray TubeFor exposure times be reduced to aminimum, the X-ray tube shall have a target that produces ahigh flux of white X-radiation and the detector shall besensitive to the X-ray energies produced Charge-CoupledDevice (CCD)- and complem

19、entary metaloxidesemiconduc-tor (CMOS)-based detectors are normally suitable for thistask. Tungsten and molybdenum target X-ray tubes are typi-cally used when collecting LAUE images. The X-ray tubepower used is dependent on the detector sensitivity and theaccelerating voltage normally varies from 20

20、 to 50 kV depend-ing on the saturation of the detector and the image quality.5.2 Back-Reflection Laue X-Ray DetectorThe Laue detec-tors can be of different types and should be sized such that asufficient number of LAUE spots are collected in one contigu-ous image. The pinhole is usually sized to abo

21、ut 6 mm about14 in. in diameter or less when possible. The camera-to-sample distance should be adjustable to accommodate theapplication, the component geometry, and the detector windowsize; it is usually set to minimum of 30 mm 1.2 in. and up to60 mm 2.4 in. These parts may be assembled in variousco

22、nfigurations depending upon the type of specimen beingstudied and the accuracy desired. For back-reflection systems,the main requirement for accurate results is that the pinholesystem shall be precisely perpendicular to the detector. Forside-reflection systems, the specimen surface shall be alignedp

23、recisely perpendicular to the bisector of the incident beampinhole and the normal of the detector plane. Adjustment foraccurate alignment of the specimen, incident beam pinhole,and the detector plane should be available on the instrument.5.3 The acquired Laue images can be of different orientationde

24、pending on the sense of the projection. Two main Laueimage orientations can be found on different instrumentsdepending on the convention or the view direction selected;first view when looking at the detector from the sample andsecond view when looking at the sample from the detector.Some software al

25、lows the view to flip to accommodate anyconvention.NOTE 1Fig. 1 illustrates a back-reflection Laue camera constructedfor use with single-crystal materials. The specimen-to-detector distance isfixed at 30 mm 1.2 in. and the specimen surface is maintainedperpendicular to the incident beam and parallel

26、 to the detector plane.NOTE 2Fig. 2 illustrates a side-reflection Laue camera for turbineblade single-crystal measurement. The measurements for this type ofsetting are limited to cubic symmetries.6. Test Specimen6.1 The test specimen may be of any convenient size orshape. Normally, the orientation w

27、ill be determined withreference to a prepared surface and a line on this surface.Surfaces on metal crystals may be prepared by methodsordinarily used in preparing metallographic specimens (Note3). After final polishing, the specimen shall be etched deeplyenough to remove all polishing distortion. Th

28、is surface shall beexamined microscopically to make sure that the etching hasremoved all scratches or distorted metal. Strain-free surfaces ofaluminum, iron, copper, brass, tungsten, nickel, etc., are easilyprepared. Great care is needed in preparing surfaces on crystalsof metals such as tin and zin

29、c (or their solid solutions), whichtwin readily on being plastically deformed. For other applica-tions that do not require high accuracy, the sample surface canbe prepared by other means or left as-manufactured.NOTE 3Reference may be made to Methods E3, for procedures forpolishing specimens.7. Proce

30、dure7.1 Laue Instrument Calibration:7.1.1 It is necessary that the orientation relationships be-tween the specimen and detector window be accurately knownat the outset (a sketch of this relationship should be made) andpreserved throughout the determinations. For example, thisrelationship is fixed if

31、 (1) the exposed specimen surface isparallel to the plane of the detector window, (2) a vertical lineinscribed on the specimen surface is parallel to a vertical lineon the detector, (3) the “top” of the detector corresponds withthe “top” of the specimen, and (4) the exposed surface of thedetector fa

32、cing the specimen is definitely marked. To verifyaccurately the alignment of the apparatus, a Laue image shouldbe collected on a known single-crystal reference before mea-suring the specimen of interest. This single-crystal referencecan be considered as a standard reference and should becertified fo

33、r use on all Laue instruments before testing. Manyinstruments include a calibration routine using a single-crystalsilicon standard.FIG. 1 Back-Reflection Laue Camera Measuring Sapphire Single Crystal Mounted on a Five-Axis Motorized GoniometerE82/E82M 1427.1.2 The calibration can be performed using

34、a simulatedpattern overlapped on top of the collected Laue image. The keyspots should match accurately. If the pattern cannot bematched, a series of parameters can be adjusted to account forthe offsets angles and distances. The parameters of interest are:the two main rotations (,), that is, up/down

35、and right/left andthe distance from the sample to the detector. This informationshould be sufficient if the detector is properly calibrated by themanufacturer.7.1.3 To verify the accuracy of the measured angles (,)and the direction, one can repeat the measurement on a knowncalibrated specimen tilted

36、 at different levels of (,) using athree-way goniometer fixture. The measured values using thematching overlay pattern should match the manually setangles.7.2 Back-Reflection Laue Pattern:7.2.1 Classical MethodThe back-reflection Laue pattern,properly prepared, will contain hundreds of diffraction s

37、pots.These spots represent “diffraction” of the X-ray beam from allimportant lattice planes of the crystal that are in positionssuitable to diffract onto the detector. The subsequent diffractionpattern obtained will consist of many spots positioned onhyperbolic curves that represent crystallographic

38、 zones. Someof these hyperbolic curves are more prominent (more thicklypopulated with spots) than others, as they represent crystallo-graphic zones having a higher population of low-index planes.By using these observations and calculating the positions of thespots using the hyperbolic chart, one can

39、 determine theorientation of the crystal with respect to the specimen referenceframe. Some programs still exist to help calculate the orienta-tion using the zone hyperbolas but they are time-consuming touse.7.2.2 Simulation MethodThis method was developed inthe last few decades and is being used mor

40、e and morefrequently; it would not be practical without the help of modernhigh-speed computers. The simulation method is both fast andaccurate. The positions and intensities of the simulated Lauespots displayed in the overlay are calculated taking intoaccount both the intensity and the extinction co

41、nditions calcu-lated from the cell parameters input for the selected spacegroup, the eleven Laue classes, or the Bravais symmetries.7.2.2.1 Two approaches have been developed for analyzingLaue data using simulation:(1) Manual matching or semi-automated matching inwhich the simulated pattern is gener

42、ated on top of theexperimentally obtained Laue image and the operator manuallyadjusts the position of the simulated Laue pattern to match theexperimentally obtained Laue image by incrementing therotation angles using a three-dimensional (3D) mouse. Thistechnique can be very accurate and fast at exec

43、ution and issometimes preferred when the material condition in the speci-men results in an unclear/less than ideal Laue image.(2) Automatic matchingThe simulated Laue pattern iscalculated from the positions of the spots defined in space andthe optimal solution is determined on the basis of the orien

44、ta-tion angles calculated from a “best match” to the experimen-tally obtained Laue image. These algorithms require extensivecalculation and the analysis can sometimes be slow, even withmodern high-speed computers.7.2.3 The pattern rotation is programmed such that the axesof rotation are with respect

45、 to the sample holder referenceframe (X, Y, Z). Alternatively, the rotations can be referencedwith respect to the 001 axes of the crystal reference frame.Additional rotation axes can be defined if required.NOTE 4Fig. 3 shows a simulated Laue pattern on top of a Laue imagecollected on a sample.7.3 In

46、dexation of Back-Reflection Laue Patterns:7.3.1 Most commercially available programs are capable ofcalculating and displaying indices of Laue spots. This is doneusing routines developed according to the crystal symmetry ofthe specimen. While some programs can display the directionsof the planes, oth

47、ers can display the (hkl) planes foreach spot. The indices are automatically displayed for the maindirections such as: , , and and, if the crystalis face-centered cubic, the projection shall include all the spotsof the forms 100, 110, 111, and 113; if body-centeredcubic, the projection shall include

48、 100, 110, 111, and112. Other directions are user selectable.7.3.2 After some experience has been gained, it is possibleto solve a Laue pattern by visual inspection of the imagedisplayed alone. The following remarks should be of assistanceFIG. 2 Side-Reflection Laue Camera for Turbine Blade Single-C

49、rystal MeasurementsE82/E82M 143in the development of a systematic approach: At least onestandard stereographic projection5of the lattice being studiedshall be prepared. This projection shall include the , and zones, and if the crystal is face-centeredcubic, the projection shall include all of the spots of the forms100, 110, 111, and 113; if body-centered cubic, theprojection shall include 100, 110, 111, and 112. Thisstandard projection shall be studied until one has becomefamiliar with the relative positions of