Electron backscatter diffraction: Difference between revisions

Revision as of 07:12, 13 November 2023

Revision as of 07:13, 13 November 2023

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These measurements do not provide information about the hydrostatic or [[volumetric strain]]s,<ref name=":5" /><ref name=":6" /> because there is no change in the orientations of lattice planes (crystallographic directions), but only changes in the position and width of the Kikuchi bands.<ref name="EBSD Image Quality Mapping">{{Cite journal |journal=Microscopy and Microanalysis |doi=10.1017/s1431927606060090 |title=EBSD Image Quality Mapping |year=2006 |last1=Wright |first1=Stuart I. |last2=Nowell |first2=Matthew M. |volume=12 |issue=1 |pages=72–84 |pmid=17481343 |bibcode=2006MiMic..12...72W |s2cid=35055001 |doi-access=free }}</ref><ref>{{Cite journal |last1=Jiang |first1=Jun |last2=Zhang |first2=Tiantian |last3=Dunne |first3=Fionn P. E. |last4=Britton |first4=T. Ben |date= 2016 |title=Deformation compatibility in a single crystalline Ni superalloy |journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |volume=472 |issue=2185 |pages=20150690 |doi=10.1098/rspa.2015.0690 |pmc=4786046 |pmid=26997901|bibcode=2016RSPSA.47250690J }}</ref>

=== The reference pattern problem ===

Nonetheless, in HR-EBSD analysis, the lattice distortion field is still calculated relative to a reference pattern or point (EBSP₀) per grain in the map, and is dependent on the lattice distortion at the point. The lattice distortion field in each grain is measured with respect to this point; therefore, the absolute lattice distortion at the reference point (relative to the unstrained crystal) is excluded from the HR-EBSD elastic strain and rotation maps.<ref name=":8">{{Cite journal |last1=Maurice |first1=Claire |last2=Fortunier |first2=Roland |last3=Driver |first3=Julian |last4=Day |first4=Austin |last5=Mingard |first5=Ken |last6=Meaden |first6=Graham |date=2010 |title=Comments on the paper "Bragg's law diffraction simulations for electron backscatter diffraction analysis" by Josh Kacher, Colin Landon, Brent L. Adams & David Fullwood |journal=Ultramicroscopy |volume=110 |issue=7 |pages=758–759 |doi=10.1016/j.ultramic.2010.02.003 |pmid=20223590 }}</ref><ref name=":9">{{Cite journal |last1=Mikami |first1=Yoshiki |last2=Oda |first2=Kazuo |last3=Kamaya |first3=Masayuki |last4=Mochizuki |first4=Masahito |date=2015 |title=Effect of reference point selection on microscopic stress measurement using EBSD |journal=Materials Science and Engineering: A |volume=647 |pages=256–264 |doi=10.1016/j.msea.2015.09.004}}</ref> This ‘reference pattern problem’ is similar to the ‘d₀ problem’ in X-ray diffraction,<ref name=":20" /><ref>{{Cite journal |last1=Koko |first1=A. |last2=Earp |first2=P. |last3=Wigger |first3=T. |last4=Tong |first4=J. |last5=Marrow |first5=T. J. |date=2020 |title=J-integral analysis: An EDXD and DIC comparative study for a fatigue crack |journal=International Journal of Fatigue |volume=134 |pages=105474 |doi=10.1016/j.ijfatigue.2020.105474 |s2cid=214391445 |url=https://researchportal.port.ac.uk/portal/en/publications/jintegral-analysis-an-edxd-and-dic-comparative-study-for-a-fatigue-crack(ccf37f3f-1a30-493e-86ea-d1ecab4fee2f).html |access-date=20 March 2023 |archive-date=27 January 2021 |archive-url=https://web.archive.org/web/20210127070347/https://researchportal.port.ac.uk/portal/en/publications/jintegral-analysis-an-edxd-and-dic-comparative-study-for-a-fatigue-crack(ccf37f3f-1a30-493e-86ea-d1ecab4fee2f).html |url-status=live }}</ref> and affects the nominal magnitude of HR-EBSD stress fields. However, selecting the reference pattern (EBSP₀) plays a key role, as severely deformed EBSP₀ adds phantom lattice distortions to the map values, thus, decreasing the measurement precision.<ref name=":8" />[[File:Linear correlation coefficients between the local conditions at the EBSP0 point and the averaged conditions.svg|thumb|Linear correlation coefficients between the local conditions at the EBSP0 point and the averaged conditions at the grain for the [[Ferrite (magnet)|ferrite]] (Fe-α) and [[austenite]] (Fe-γ) phase of [[age-hardened DSS]], and [[Silicon]] (Si). The analysis considers the average deformation gradient tensor determinant (<math>A^{0}</math>), maximum in-plane principal strain (<math>\epsilon_{MAX}</math>), rotation magnitude (<math>\omega_{T}=\sqrt(\omega_{32}^2+\omega_{13}^2+\omega_{21}^2)</math>), correlation peak height (PH), mean angular error (MAE) and GND density.<ref name=":10" />|272x272px300x300px|alt=Linear correlation coefficients between the local conditions at the EBSP0 point and the averaged conditions at the grain for the ferrite (Fe-α) and austenite (Fe-γ) phase of age-hardened DSS, and Silicon (Si). The analysis considers the average deformation gradient tensor determinant, maximum in-plane principal strain, rotation magnitude, correlation peak height, mean angular error and GND density.]]

The local lattice distortion at the EBSP₀ influences the resultant HR-EBSD map, e.g., a reference pattern deformed in tension will directly reduce the HR-EBSD map tensile strain magnitude while indirectly influencing the other component magnitude and the strain's spatial distribution. Furthermore, the choice of EBSP₀ slightly affects the GND density distribution and magnitude, and choosing a reference pattern with a higher GND density reduces the cross-correlation quality, changes the spatial distribution and induces more errors than choosing a reference pattern with high lattice distortion. Additionally, there is no apparent connection between EBSP₀’s IQ and EBSP₀'s local lattice distortion.<ref name=":10" />