ASTM E82/E82M-14(2019)
(Test Method)Standard Test Method for Determining the Orientation of a Metal Crystal
Standard Test Method for Determining the Orientation of a Metal Crystal
SIGNIFICANCE AND USE
4.1 The physical properties of metals and other materials are often anisotropic (for example: Young's modulus will typically vary in different crystallographic directions). As such, it is often desirable or necessary to determine the orientation of a single crystal to ascertain the relation of any pertinent physical properties with respect to different directions in the material.
4.2 This test method can be used commercially as a quality control test in production situations in which a desired orientation, within prescribed limits, is required.
4.3 With the use of an adjustable, fixed holder that can later be mounted on a saw, lathe, or other machine, a single crystal material can be moved to a preferred orientation and subsequently sectioned, ground, or processed otherwise.
4.4 If the grains in a polycrystalline material are large enough, this test method can also be used to determine their orientations and differences in orientation can be documented or mapped or both.
SCOPE
1.1 This test method covers the back-reflection Laue procedure for determining the orientation of a metal crystal. The back-reflection Laue method for determining crystal orientation may be applied to macrograins and micrograins depending on the beam size within polycrystalline aggregates, as well as to single crystals of any size. This test method is described with reference to cubic crystals and other structures such as: hexagonal, tetragonal, or orthorhombic crystals.
1.2 Most natural crystals have well developed external faces, and the orientation of such crystals can usually be determined from inspection. The orientation of a crystal having poorly developed faces or no faces at all (for example, a metal crystal prepared in the laboratory) shall be determined by more elaborate methods. The most convenient and accurate of these involves the use of X-ray diffraction. The “orientation of a metal crystal” is known when the positions in space of the crystallographic axes of the unit cell have been located with reference to the surface geometry of the crystal specimen. This relation between unit cell position and surface geometry is most conveniently expressed by stereographic or gnomonic projection.
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system 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 the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E82/E82M −14 (Reapproved 2019)
Standard Test Method for
Determining the Orientation of a Metal Crystal
This standard is issued under the fixed designation E82/E82M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This test method covers the back-reflection Laue proce-
Barriers to Trade (TBT) Committee.
dure for determining the orientation of a metal crystal. The
back-reflection Laue method for determining crystal orienta-
2. Referenced Documents
tion may be applied to macrograins and micrograins depending
on the beam size within polycrystalline aggregates, as well as
2.1 ASTM Standards:
tosinglecrystalsofanysize.Thistestmethodisdescribedwith E3 Guide for Preparation of Metallographic Specimens
reference to cubic crystals and other structures such as:
hexagonal, tetragonal, or orthorhombic crystals. 3. Summary of Test Method
1.2 Most natural crystals have well developed external
3.1 Thearrangementoftheapparatusissimilartothatofthe
3,4
faces, and the orientation of such crystals can usually be transmissionLauemethodforcrystalstructuredetermination
determinedfrominspection.Theorientationofacrystalhaving
except that the detector is located between the X-ray source
poorly developed faces or no faces at all (for example, a metal and the specimen or beside the X-ray source in the case of side
crystal prepared in the laboratory) shall be determined by more
reflection geometry. The incident beam of white X-radiation
elaborate methods. The most convenient and accurate of these passes through a pinhole aperture, strikes the crystal, and is
involves the use of X-ray diffraction. The “orientation of a
then diffracted back to the detector. White spots, which
metal crystal” is known when the positions in space of the representX-raybeams“diffracted”bytheatomicplaneswithin
crystallographic axes of the unit cell have been located with
the crystalline specimen, appear on the digital picture collected
reference to the surface geometry of the crystal specimen. This by the detector. The indexation of the spots and their positions
relation between unit cell position and surface geometry is
in space are calculated by simulation of the Laue pattern
most conveniently expressed by stereographic or gnomonic superimposed onto the digital image collected by the detector.
projection.
Older techniques based on film technology can also be used to
index the spots and to calculate the orientation of the crystal.
1.3 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as standard. The
4. Significance and Use
values stated in each system may not be exact equivalents;
therefore,eachsystemshallbeusedindependentlyoftheother.
4.1 Thephysicalpropertiesofmetalsandothermaterialsare
Combining values from the two systems may result in non-
often anisotropic (for example:Young’s modulus will typically
conformance with the standard.
vary in different crystallographic directions). As such, it is
often desirable or necessary to determine the orientation of a
1.4 This standard does not purport to address all of the
single crystal to ascertain the relation of any pertinent physical
safety concerns, if any, associated with its use. It is the
properties with respect to different directions in the material.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4.2 This test method can be used commercially as a quality
mine the applicability of regulatory limitations prior to use.
control test in production situations in which a desired
1.5 This international standard was developed in accor-
orientation, within prescribed limits, is required.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This test method is under the jurisdiction of ASTM Committee E04 on Standards volume information, refer to the standard’s Document Summary page on
Metallography and is the direct responsibility of Subcommittee E04.11 on X-Ray the ASTM website.
and Electron Metallography. Cullity, B. D., Elements of X-ray Diffraction, second edition, Addison-Wesley,
Current edition approved Nov. 1, 2019. Published November 2019. Originally Reading, MA, 1978.
approved in 1949. Last previous edition approved in 2014 as E82/E82M–14. DOI: Barrett, C. S. and Massalski, T. B., The Structure of Metals, 3rd edition,
10.1520/E0082_E0082M-14R19. McGraw-Hill Inc., New York, 1966, pp. 211–227.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E82/E82M − 14 (2019)
4.3 With the use of an adjustable, fixed holder that can later second view when looking at the sample from the detector.
be mounted on a saw, lathe, or other machine, a single crystal Some software allows the view to flip to accommodate any
material can be moved to a preferred orientation and subse- convention.
NOTE 1—Fig. 1 illustrates a back-reflection Laue camera constructed
quently sectioned, ground, or processed otherwise.
for use with single-crystal materials. The specimen-to-detector distance is
4.4 If the grains in a polycrystalline material are large
fixed at 30 mm [1.2 in.] and the specimen surface is maintained
enough, this test method can also be used to determine their perpendicular to the incident beam and parallel to the detector plane.
NOTE 2—Fig. 2 illustrates a side-reflection Laue camera for turbine
orientations and differences in orientation can be documented
blade single-crystal measurement. The measurements for this type of
or mapped or both.
setting are limited to cubic symmetries.
5. Apparatus
6. Test Specimen
5.1 X-Ray Tube—For exposure times be reduced to a
6.1 The test specimen may be of any convenient size or
minimum, the X-ray tube shall have a target that produces a
shape. Normally, the orientation will be determined with
high flux of white X-radiation and the detector shall be
reference to a prepared surface and a line on this surface.
sensitive to the X-ray energies produced [Charge-Coupled
Surfaces on metal crystals may be prepared by methods
Device (CCD)- and complementary metal–oxide–semiconduc-
ordinarily used in preparing metallographic specimens (Note
tor (CMOS)-based detectors are normally suitable for this
3). After final polishing, the specimen shall be etched deeply
task]. Tungsten and molybdenum target X-ray tubes are typi-
enough to remove all polishing distortion.This surface shall be
cally used when collecting LAUE images. The X-ray tube
examined microscopically to make sure that the etching has
power used is dependent on the detector sensitivity and the
removedallscratchesordistortedmetal.Strain-freesurfacesof
accelerating voltage normally varies from 20 to 50 kVdepend-
aluminum, iron, copper, brass, tungsten, nickel, etc., are easily
ing on the saturation of the detector and the image quality.
prepared.Greatcareisneededinpreparingsurfacesoncrystals
5.2 Back-Reflection Laue X-Ray Detector—The Laue detec- of metals such as tin and zinc (or their solid solutions), which
tors can be of different types and should be sized such that a twin readily on being plastically deformed. For other applica-
sufficient number of LAUE spots are collected in one contigu- tions that do not require high accuracy, the sample surface can
ous image. The pinhole is usually sized to about 6 mm [about be prepared by other means or left as-manufactured.
⁄4 in.] in diameter or less when possible. The camera-to-
NOTE 3—Reference may be made to Methods E3, for procedures for
sample distance should be adjustable to accommodate the
polishing specimens.
application, the component geometry, and the detector window
size; it is usually set to minimum of 30 mm [1.2 in.] and up to 7. Procedure
60 mm [2.4 in.]. These parts may be assembled in various
7.1 Laue Instrument Calibration:
configurations depending upon the type of specimen being
7.1.1 It is necessary that the orientation relationships be-
studied and the accuracy desired. For back-reflection systems,
tween the specimen and detector window be accurately known
the main requirement for accurate results is that the pinhole
at the outset (a sketch of this relationship should be made) and
system shall be precisely perpendicular to the detector. For
preserved throughout the determinations. For example, this
side-reflection systems, the specimen surface shall be aligned
relationship is fixed if (1) the exposed specimen surface is
precisely perpendicular to the bisector of the incident beam
parallel to the plane of the detector window, (2) a vertical line
pinhole and the normal of the detector plane. Adjustment for
inscribed on the specimen surface is parallel to a vertical line
accurate alignment of the specimen, incident beam pinhole,
on the detector, (3) the “top” of the detector corresponds with
and the detector plane should be available on the instrument.
the “top” of the specimen, and (4) the exposed surface of the
5.3 TheacquiredLaueimagescanbeofdifferentorientation detector facing the specimen is definitely marked. To verify
depending on the sense of the projection. Two main Laue accurately the alignment of the apparatus, a Laue image should
image orientations can be found on different instruments be collected on a known single-crystal reference before mea-
depending on the convention or the view direction selected; suring the specimen of interest. This single-crystal reference
first view when looking at the detector from the sample and can be considered as a standard reference and should be
FIG. 1 Back-Reflection Laue Camera Measuring Sapphire Single Crystal Mounted on a Five-Axis Motorized Goniometer
E82/E82M − 14 (2019)
FIG. 2 Side-Reflection Laue Camera for Turbine Blade Single-Crystal Measurements
certified for use on all Laue instruments before testing. Many lated from the cell parameters input for the selected space
instruments include a calibration routine using a single-crystal group, the eleven Laue classes, or the Bravais symmetries.
silicon standard.
7.2.2.1 Two approaches have been developed for analyzing
7.1.2 The calibration can be performed using a simulated
Laue data using simulation:
patternoverlappedontopofthecollectedLaueimage.Thekey
(1) Manual matching or semi-automated matching in
spots should match accurately. If the pattern cannot be
which the simulated pattern is generated on top of the
matched, a series of parameters can be adjusted to account for
experimentallyobtainedLaueimageandtheoperatormanually
the offsets angles and distances.The parameters of interest are:
adjusts the position of the simulated Laue pattern to match the
the two main rotations (α,β), that is, up/down and right/left and
experimentally obtained Laue image by incrementing the
the distance from the sample to the detector. This information
rotation angles using a three-dimensional (3D) mouse. This
should be sufficient if the detector is properly calibrated by the
technique can be very accurate and fast at execution and is
manufacturer.
sometimes preferred when the material condition in the speci-
7.1.3 To verify the accuracy of the measured angles (α,β,γ)
men results in an unclear/less than ideal Laue image.
and the direction, one can repeat the measurement on a known
(2) Automatic matching—The simulated Laue pattern is
calibrated specimen tilted at different levels of (α,β,γ) using a
calculated from the positions of the spots defined in space and
three-way goniometer fixture. The measured values using the
the optimal solution is determined on the basis of the orienta-
matching overlay pattern should match the manually set
tion angles calculated from a “best match” to the experimen-
angles.
tally obtained Laue image. These algorithms require extensive
calculation and the analysis can sometimes be slow, even with
7.2 Back-Reflection Laue Pattern:
modern high-speed computers.
7.2.1 Classical Method—The back-reflection Laue pattern,
7.2.3 The pattern rotation is programmed such that the axes
properly prepared, will contain hundreds of diffraction spots.
of rotation are with respect to the sample holder reference
These spots represent “diffraction” of the X-ray beam from all
frame (X, Y, Z). Alternatively, the rotations can be referenced
important lattice planes of the crystal that are in positions
with respect to the [001] axes of the crystal reference frame.
suitabletodiffractontothedetector.Thesubsequentdiffraction
Additional rotation axes can be defined if required.
pattern obtained will consist of many spots positioned on
hyperbolic curves that represent crystallographic zones. Some
NOTE 4—Fig. 3 shows a simulated Laue pattern on top of a Laue image
of these hyperbolic curves are more prominent (more thickly
collected on a sample.
populated with spots) than others, as they represent crystallo-
7.3 Indexation of Back-Reflection Laue Patterns:
graphic zones having a higher population of low-index planes.
7.3.1 Most commercially available programs are capable of
Byusingtheseobservationsandcalculatingthepositionsofthe
calculating and displaying indices of Laue spots. This is done
spots using the hyperbolic chart, one can determine the
using routines developed according to the crystal symmetry of
orientationofthecrystalwithrespecttothespecimenreference
the specimen. While some programs can display the directions
frame. Some programs still exist to help calculate the orienta-
of the planes, others can display the (hkl) planes for
tion using the zone hyperbolas but they are time-consuming to
each spot.The indices are automatically displayed for the main
use.
directionssuchas:<100>,<100>,and<111>and,ifthecrystal
7.2.2 Simulation Method—This method was developed in
is face-centered cubic, the projection shall include all the spots
the last few decades and is being used more and more
of the forms {100}, {110}, {111}, and {113}; if body-centered
frequently;itwouldnotbepracticalwithoutthehelpofmodern
cubic, the projection shall include {100}, {110}, {111}, and
high-speed computers. The simulation m
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.