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arXiv 2203.17015cond-mat.mtrl-sci
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布拉格相干X射线衍射成像的改进:电子背散射衍射对准和应变场计算

Refinements for Bragg coherent X-ray diffraction imaging: Electron backscatter diffraction alignment and strain field computation

David Yang, Mark T. Lapington, Guanze He, Kay Song, Minyi Zhang, Clara Barker, Ross J. Harder, Wonsuk Cha, Wenjun Liu, Nicholas W. Phillips, Felix Hofmann

摘要:

布拉格相干X射线衍射成像(BCDI)允许沿着特定微晶的散射矢量对晶格应变进行三维(3D)测量。如果测量至少三个线性独立的反射,则可以恢复微晶内的全晶格应变张量的3D变化。然而,这需要晶体取向的知识,这通常通过基于晶体几何形状或同步加速器微束劳厄衍射测量的估计来获得。在这里,我们提出了一种替代的方法来确定晶体取向的BCDI测量,通过使用电子背散射衍射(EBSD)在三个不同的基板上对齐Fe-Ni和Co-Fe合金微晶。从EBSD欧拉角计算取向矩阵,并与使用微束劳厄衍射确定的取向进行比较。取向矩阵之间的平均角度失配小于~6度,这对于布拉格反射的搜索是合理的。我们证明了使用来自EBSD取向矩阵对准和测量五个反射为一个单一的Fe-Ni微晶使用多反射BCDI。利用该数据集,开发了基于相位复指数梯度的精细应变场计算。这种方法被证明可以提高精度,特别是在存在位错的情况下。我们的研究结果表明,使用EBSD预对准BCDI样品和更有效的方法来确定晶格应变张量具有更高的精度的应用程序的可行性。

英文摘要:

Bragg coherent X-ray diffraction imaging (BCDI) allows the three-dimensional (3D) measurement of lattice strain along the scattering vector for specific microcrystals. If at least three linearly independent reflections are measured, the 3D variation of the full lattice strain tensor within the microcrystal can be recovered. However, this requires knowledge of the crystal orientation, which is typically attained via estimates based on crystal geometry or synchrotron micro-beam Laue diffraction measurements. Here, we present an alternative method to determine the crystal orientation for BCDI measurements, by using electron backscatter diffraction (EBSD) to align Fe-Ni and Co-Fe alloy microcrystals on three different substrates. The orientation matrix is calculated from EBSD Euler angles and compared to the orientation determined using micro-beam Laue diffraction. The average angular mismatch between the orientation matrices is less than ~6 degrees, which is reasonable for the search for Bragg reflections. We demonstrate the use of an orientation matrix derived from EBSD to align and measure five reflections for a single Fe-Ni microcrystal using multi-reflection BCDI. Using this dataset, a refined strain field computation based on the gradient of the complex exponential of the phase is developed. This approach is shown to increase accuracy, especially in the presence of dislocations. Our results demonstrate the feasibility of using EBSD to pre-align BCDI samples and the application of more efficient approaches to determine the lattice strain tensor with greater accuracy.

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