A look-up table based approach to characterize crystal twinning for synchrotron X-ray Laue microdiffraction scans

Li, Yao; Wan, Lijuan; Chen, Kai

doi:10.1107/s1600576715004896

Cited by 19 publications

(9 citation statements)

References 45 publications

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“…For example, to measure crystal orientation, elastic strain distribution 32 , to distinguish between statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs) 33 , to characterize the slip system of the GNDs 34 , to quantify dislocation densities 35 , one still needs to index the Laue pattern and analyze peak shape the usual way. Furthermore, although we demonstrate that the low angle grain boundaries are visible in the FIM, it is noted that from the FIM solely, it is difficult to distinguish between phase boundaries, low angle grain boundaries, high angle grain boundaries, and twin boundaries, and therefore it is necessary to index the Laue patterns 36 . An example containing both low and high angle grain boundaries is shown in Section 2 of the supplementary information .…”

Section: Discussionmentioning

confidence: 68%

Real-time microstructure imaging by Laue microdiffraction: A sample application in laser 3D printed Ni-based superalloys

Zhou

Zhu

Shen

et al. 2016

Sci Rep

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Synchrotron-based Laue microdiffraction has been widely applied to characterize the local crystal structure, orientation, and defects of inhomogeneous polycrystalline solids by raster scanning them under a micro/nano focused polychromatic X-ray probe. In a typical experiment, a large number of Laue diffraction patterns are collected, requiring novel data reduction and analysis approaches, especially for researchers who do not have access to fast parallel computing capabilities. In this article, a novel approach is developed by plotting the distributions of the average recorded intensity and the average filtered intensity of the Laue patterns. Visualization of the characteristic microstructural features is realized in real time during data collection. As an example, this method is applied to image key features such as microcracks, carbides, heat affected zone, and dendrites in a laser assisted 3D printed Ni-based superalloy, at a speed much faster than data collection. Such analytical approach remains valid for a wide range of crystalline solids, and therefore extends the application range of the Laue microdiffraction technique to problems where real-time decision-making during experiment is crucial (for instance time-resolved non-reversible experiments).

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Section: Discussionmentioning

confidence: 68%

Real-time microstructure imaging by Laue microdiffraction: A sample application in laser 3D printed Ni-based superalloys

Zhou

Zhu

Shen

et al. 2016

Sci Rep

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“…In the polycrystalline region, the grains on the right side, which are closer to the edge of the specimen, are as narrow as 10–20 μm in the X -direction but elongated to up to 80 μm in Y -direction, while most of the grains farther away from the specimen edge are nearly equiaxed, with grain size ranging from 20 to 60 μm. Applying the approached developed previously 16 , we found that most of grain boundaries in this area are ordinary high angle ones, while twinning structures are only detected in a few grains.…”

Section: Resultsmentioning

confidence: 76%

A synchrotron study of microstructure gradient in laser additively formed epitaxial Ni-based superalloy

Xue

Zhang

et al. 2015

Sci Rep

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Laser additive forming is considered to be one of the promising techniques to repair single crystal Ni-based superalloy parts to extend their life and reduce the cost. Preservation of the single crystalline nature and prevention of thermal mechanical failure are two of the most essential issues for the application of this technique. Here we employ synchrotron X-ray microdiffraction to evaluate the quality in terms of crystal orientation and defect distribution of a Ni-based superalloy DZ125L directly formed by a laser additive process rooted from a single crystalline substrate of the same material. We show that a disorientation gradient caused by a high density of geometrically necessary dislocations and resultant subgrains exists in the interfacial region between the epitaxial and stray grains. This creates a potential relationship of stray grain formation and defect accumulation. The observation offers new directions on the study of performance control and reliability of the laser additive manufactured superalloys.

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“…The misorientation angle between the MC particles and matrix ranges from 5 to 60° (Fig. 1g), implying the incoherent nature of the boundaries between MC particles and γ/γ′ phase [27,28]. Both of the two grain boundaries observed in the studied region are tilt grain boundaries, and the misorientation angles are about 24°and 17°, respectively.…”

Section: Microstructural Characterization Near the Crack Regionmentioning

confidence: 99%

Mechanism of heat affected zone cracking in Ni-based superalloy DZ125L fabricated by laser 3D printing technique

Chen

Tamura

2018

Materials & Design

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• The heat affected zone cracking initiates due to the re-melting of preexisting intergranular γ/γ′ eutectics and coarse γ′.• The transverse tensile strain/stress causing the initiation and propagation of crack is quantitatively measured.• The micro-size MC carbides are considered to be a possible contributor to the hot cracking initiation. Laser 3D printing is a promising technique to repair damaged Ni-based superalloy components. However, the occurrence of heat affected zone (HAZ) cracking severely limits its applicability. Here we unravel the cracking mechanism by studying the element, phase, defect, and strain distribution around an intergranular crack that initiated from the primary HAZ. Using synchrotron X-ray Laue microdiffraction, we measured high tensile strain/ stress transverse to the building direction in both the primary HAZ and the cladding layers, as well as highdensity dislocations, which resulted from the thermal contraction and rapid precipitation of γ′ phase. The crack initiated because the transverse tensile strain/stress tore up the liquid film formed by the low-melting point preexisting phases in the primary HAZ, such as γ/γ′ eutectics and coarse γ′ precipitates. The incoherent carbide particles were frequently observed near the crack root as local strain concentrators. In the cladding layers, micro-segregation could not be completely avoided, thus the hot crack continued to propagate over several layers with the assistance of the transverse tensile stress. Our investigations provide a useful guideline for the optimization of the 3D printing process to repair Ni-based superalloys with high susceptibility to hot cracking.

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A look-up table based approach to characterize crystal twinning for synchrotron X-ray Laue microdiffraction scans

Cited by 19 publications

References 45 publications

Real-time microstructure imaging by Laue microdiffraction: A sample application in laser 3D printed Ni-based superalloys

Real-time microstructure imaging by Laue microdiffraction: A sample application in laser 3D printed Ni-based superalloys

A synchrotron study of microstructure gradient in laser additively formed epitaxial Ni-based superalloy

Mechanism of heat affected zone cracking in Ni-based superalloy DZ125L fabricated by laser 3D printing technique

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