Quantitative assessment of the driving force for twin formation utilizing Nye tensor dislocation density mapping

Leff, Asher C.; Taheri, Mitra L.

doi:10.1016/j.scriptamat.2016.04.035

Cited by 10 publications

(4 citation statements)

References 29 publications

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“…The series observation indicates that SIBM starts in some of the highest stress areas rather than in all stored energy areas, and then spreads out to other stressed regions step by step, similar results have been observed by Shun Tokita [19]. Additionally, numerous long, parallel and coherent Σ3 boundaries are formed in region A and B after SIBM takes place in these regions, which is consistent with the growth accident model of twin generation [20]. Since all the areas with new-formed twins inside exhibit a lower stored energy than other unchanged parts from the local misorientation maps in Fig.…”

supporting

confidence: 86%

Evolution of Grain Boundary Character Distribution in Pure Copper during Low-Strain Thermomechanical Processing

Chen

Huang

et al. 2019

MSF

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In order to get optimal grain boundary character distribution (GBCD) and grain boundary properties, thermomechanical processing (TMP) is usually adopted in grain boundary engineering. However, the mechanism behind the TMP treatments and GBCD optimization is still unclear. The present study has conducted a series experiments involving low-strain TMPs to study the relationship between TMP parameters and the behind microstructural evolution. The experimental results indicate that in the scope of low-strain TMP, strain induced boundary migration (SIBM) is the most effective process for GBCD optimization. Besides, SIBM and grain growth would gradually transfer to recrystallization with the increase of pre-deformation level and annealing temperature. Further quasi in-situ EBSD results infer that SBIM is activated locally in some region with high stored energy, and further gradual initiation of SIBM from one region to another contributes to the gradual increase of special boundaries with annealing time.

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confidence: 86%

Evolution of Grain Boundary Character Distribution in Pure Copper during Low-Strain Thermomechanical Processing

Chen

Huang

et al. 2019

MSF

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“…This technique is especially helpful in obtaining a comprehensive picture of microstructural evolution in UFG/NC metals, which are known to have an unstable microstructure [18]. Precession electron diffraction has also been used to estimate dislocation densities and driving force for twin formation using Nye tensor [27], [28].…”

Section: Introductionmentioning

confidence: 99%

Grain rotations in ultrafine-grained aluminum films studied using in situ TEM straining with automated crystal orientation mapping

Izadi

Darbal²,

Sarkar

et al. 2017

Materials & Design

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In situ TEM straining allows probing deformation mechanisms of ultrafine-grained and nanocrystalline metals. While obtaining statistically meaningful information about microstructural changes using conventional bright-field/dark-field imaging or diffraction is time consuming, automated crystal orientation mapping in TEM (ACOM-TEM) enables tracking orientation changes of hundreds of grains simultaneously. We use this technique to uncover extensive grain rotations during in situ tensile deformation of a freestanding, ultrafine-grained aluminum film (thickness 200 nm, mean grain size 180 nm). During loading, both the fraction of grains that undergo rotations and the magnitude of their rotations increase with strain. The rotations are partially or fully reversible in a significant fraction of grains during unloading, leading to notable inelastic strain recovery. More surprisingly, the direction of rotation remains unchanged for a small fraction of grains during unloading, despite a sharp reduction in the applied stress. The ACOM-TEM measurements also provide evidence of reversible and irreversible grain/twin boundary migrations in the film. These microstructural observations point to a highly inhomogeneous and constantly evolving stress distribution in the film during both loading and unloading.

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“…This analysis technique is capable of accessing both GNDs and SSDs due to the scale of the applied probe. It has been applied to the study of the effect of dislocation densities on microevolution processes such as grain rotation, boundary migration, and other microstructural transitions [34]. Maps produced using this technique are consistent with TEM images of dislocation structures taken in the analysis regions, and the dislocation density values calculated are on the same orders of magnitude with those from literature [22,35,36].…”

Section: Introductionmentioning

confidence: 60%

“…Grain rotation is just one example of a process of microstructural evolution that can be informed by this technique. The mechanism and driving force for twinning is of particular interest and is the subject of a parallel work using this methodology [34].…”

Section: Dislocation Motion and Dislocation-driven Processesmentioning

confidence: 99%

Estimation of dislocation density from precession electron diffraction data using the Nye tensor

2015

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The Nye tensor offers a means to estimate the geometrically necessary dislocation density of a crystalline sample based on measurements of the orientation changes within individual crystal grains. In this paper, the Nye tensor theory is applied to precession electron diffraction automated crystallographic orientation mapping (PED-ACOM) data acquired using a transmission electron microscope (TEM). The resulting dislocation density values are mapped in order to visualize the dislocation structures present in a quantitative manner. These density maps are compared with other related methods of approximating local strain dependencies in dislocation-based microstructural transitions from orientation data. The effect of acquisition parameters on density measurements is examined. By decreasing the step size and spot size during data acquisition, an increasing fraction of the dislocation content becomes accessible. Finally, the method described herein is applied to the measurement of dislocation emission during in situ annealing of Cu in TEM in order to demonstrate the utility of the technique for characterizing microstructural dynamics.

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Quantitative assessment of the driving force for twin formation utilizing Nye tensor dislocation density mapping

Cited by 10 publications

References 29 publications

Evolution of Grain Boundary Character Distribution in Pure Copper during Low-Strain Thermomechanical Processing

Evolution of Grain Boundary Character Distribution in Pure Copper during Low-Strain Thermomechanical Processing

Grain rotations in ultrafine-grained aluminum films studied using in situ TEM straining with automated crystal orientation mapping

Estimation of dislocation density from precession electron diffraction data using the Nye tensor

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