Comparison between diffraction contrast tomography and high-energy diffraction microscopy on a slightly deformed aluminium alloy

Abstract

The grain structure of an Al-0.3 wt%Mn alloy deformed to 1% strain was reconstructed using diffraction contrast tomography (DCT) and high-energy diffraction microscopy (HEDM). 14 equally spaced HEDM layers were acquired and their exact location within the DCT volume was determined using a generic algorithm minimizing a function of the local disorientations between the two data sets. The microstructures were then compared in terms of the mean crystal orientations and shapes of the grains. The comparison shows that DCT can detect subgrain boundaries with disorientations as low as 1 and that HEDM and DCT grain boundaries are on average 4 mm apart from each other. The results are important for studies targeting the determination of grain volume. For the case of a polycrystal with an average grain size of about 100 mm, a relative deviation of about 10% was found between the two techniques.

Evaluation of grain-average stress tensor in a tensile-deformed Al–Mn polycrystal by high-energy X-ray diffraction

“…13b) at an applied strain of 1%. A similar tendency was observed in results of finite element simulations performed on the volume reconstructed by DCT (Renversade et al, 2016), which gave 0.33 and 0.35, respectively.…”

“…orientation of grains between the DCT and 3DXRD reconstructions, the general six-dimensional registration approach introduced by Renversade et al (2016) was simplified here to the search for the optimal rotation and translation that minimize the distance between the DCT and 3DXRD grain centroids. The resultant rigid-body movement was equal to a translation vector of [À5, À5, À11] (mm) and a rotation of 0.11 with regard to the DCT frame (around an axis close to [0, 0, 1]).…”

“…All these indicate that the coherent domain size in the investigated Al-0.3 wt% Mn polycrystal is much smaller than the Pendellö sung length and the kinematic diffraction theory should apply. Evidently, the situation does not change if the crystal is deformed -only the application of classical DCT to deformed samples becomes more challenging (Viganò et al, 2014;Renversade et al, 2016). Therefore, the disagreement between DCT and 3DXRD volumes for small grains is not related to the dynamical or kinematic nature of diffraction, but probably to differences in the algorithms used for measuring peak intensity (Nervo et al, 2014).…”

Optimal polyhedral description of 3D polycrystals: Method and application to statistical and synchrotron X-ray diffraction data

“…The average error on the centroid positions (relative to the average diameter) is reduced from 10.1% to 0.7%, on the volumes (relative to the average volume) from 14.4% to 3.2% and on the diameters (relative to the average diameter) from 10.8% to 1.3%. Final values are significantly lower than the typical experimental uncertainty of a few percents [53]. It should also be noticed from Figure 14b,c that optimization leads to a significant change of morphology.…”

Bragg coherent diffractive imaging of single-grain defect dynamics in polycrystalline films

“…Thus, much focus has been placed on understanding the links between the heterogeneous grain distribution, the motion of grain boundaries, and the resulting material properties. These ongoing developments have been driven in part by the ability to nondestructively determine the grain distribution and orientation by using x-ray diffraction (8,9), including advanced techniques such as micro-Laue (10,11) and high-energy diffraction microscopy (12,13). In particular, diffraction contrast tomography has been used to study grain growth (8,14).…”