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![[Figure 3]](ui5006fig3mag.jpg)
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Figure 3
Experimental CBED patterns through two different voids in the same Al–Cu–Sn alloy specimen suggest that these two regions of the specimen have tilt projections that are related by inversion – implying that the voids in these two cases are equidistant from opposite specimen faces. (a) and (b) TEM images of the two different voids through which CBED patterns were collected at the indicated points (red dots). The voids, the associated monoatomic-thickness tin shell (Tan et al., 2021  ), the connected tin precipitate, the connected θ′ and other independent θ′ precipitates are also indicated in these images. (c) and (d) CBED patterns from the indicated locations in (a) and (b), respectively, that have been radially differentiated (Nakashima & Muddle, 2010a,b) to remove the diffuse background due to inelastic scattering (a pre-requisite for QCBED) and to make turning points in the intensity distributions more distinct. (e) and (f) The differentiated CBED patterns from (c) and (d) furnished QCBED refinements of the thicknesses of each of the regions of the matrix–void–matrix multislice models shown in (g) and (h). (g) and (h) The outcomes of these thickness refinements; the models are drawn to scale except for the off-axis tilt, which has been exaggerated for illustration. The structural tilt projections are non-centrosymmetric in both cases and are approximately inverted with respect to one another along the tilt direction, as are the corresponding intensities in the 220 reflections of (c) and (d) along the 220 scattering vector. The QCBED-measured thicknesses shown in (g) and (h) also demonstrate the approximate inverse relationship between void depths within the specimen for these two cases. Note that the total thickness of the specimen for the first case [(a), (c), (e) and (g)] is 1169 ± 1 Å and for the second case [(b), (d), (f) and (h)] is 1157 ± 2 Å. |
![[Figure 3]](ui5006fig3.jpg)
 | JOURNAL OF APPLIED CRYSTALLOGRAPHY |
ISSN: 1600-5767
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