Advanced characterization of twins using automated electron backscatter diffraction Page: 3 of 8
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boundary be near the ideal misorientation of 600 about <111>; but, the boundary plane must also be
oriented so that it is aligned with the 11111 planes in the adjoining crystals.
While OIM makes it relatively easy to measure grain boundary misorientations, the
measurement of boundary plane orientations is not as straightforward. The orientation of individual
grain boundary planes can be measured using either serial sectioning  or by observation of grain
boundaries appearing on two mutually perpendicular sections  (i.e. at the sample edges). A
statistical distribution of boundary plane orientations can also be obtained using stereology by
sectioning on oblique planes. While such studies can provide a complete description of all five
geometrical boundary parameters (three for the misorientation and two the boundary plane
orientation), they are difficult to perform. However, Wright and co-workers [9, 10] have shown that
a partial description of boundary plane orientations can be obtained from OIM measurements on a
single surface plane. This technique extends that described by Randle  by matching the poles of
the misorientation-coincident planes.
Two critical parameters will be used in this study to characterize twin boundaries. The first is the
misorientation deviation or AO, which describes the angular deviation between the measured
misorientation and the ideal twin misorientation. The second parameter is the trace deviation, AOw.
The trace deviation is the angular distance between the trace of the boundary on the measured
surface and the intersection the crystallographic twinning plane makes with the sample surface. An
example of the trace deviation measure for two boundaries meeting the misorientation relationship
criterion for a twin boundary is shown in Fig. 1. The sample is nickel and delineated boundaries
correspond to the primary recrystallization twin (600 about <111>). In this figure, the white
boundaries are those which have both A6 and AOw values less than 8.70 (the A6 value prescribed by
Brandon  for this type of boundary). The black boundaries are those boundaries with A6 less
than 8.70 but with AOw values greater than 8.70 degrees. Two specific boundaries have been
highlighted in the figure. The boundary marked A satisfies both criteria - AOw is 0.60. Boundary B
does not meet the trace deviation criterion - AOw equals 130. The spoked figures overlaid on the map
show the traces of 11111 boundaries within the grain. The "spokes" highlighted in white
correspond to the pair of 11111 planes whose poles are most closely oriented, that is, those whose
normals represent the common misorientation axis. If the proposition to be checked is whether or
not the trace represents the actual coherent twin, then it is these specific planes from the family of
crystallographic equivalents that should be considered for deviation from the trace. The approach
for deformation twin boundary identification and verification is similar, but in this case the
potential twinning plane is fixed for each system, and the proposition is whether or not the
candidate boundary is actually a twin.
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Wright, S. I. (Stuart I.); Bingert, J. F. (John F.); Mason, T. A. (Thomas A.) & Larson, R. J. (Ryan J.). Advanced characterization of twins using automated electron backscatter diffraction, article, January 1, 2002; United States. (https://digital.library.unt.edu/ark:/67531/metadc928035/m1/3/: accessed April 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.