Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

Li, Runguang; Xie, Qingge; Wang, Yandong; Liu, Wenjun; Wang, Mingguang; Wu, Guilin; Li, Xiaowu; Zhang, Minghe; Liu, Xiongjun; Geng, Chang; Zhu, Ting

doi:10.1073/pnas.1711994115

Cited by 61 publications

(32 citation statements)

References 28 publications

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“…We have presented the GND density distribution due to the local plasticity as a result of arrays of dislocation lines piled up against a grain boundary. The 3D resolution of the curvature field with the DAXM method provides sufficient spatial resolution (< 0.5 μm [28,45], smaller than the scanning step size) and high angular resolution (~0.01 o ) for 3D mapping of the curvature tensor. A lower bound GND density noise level can be estimated using:…”

Section: Discussionmentioning

confidence: 99%

Dislocation density distribution at slip band-grain boundary intersections

et al. 2020

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We study the mechanisms of slip transfer at a grain boundary, in titanium, using Differential Aperture X-ray Laue Micro-diffraction (DAXM). This 3D characterisation tool enables measurement of the full (9-component) Nye lattice curvature tensor and calculation of the density of geometrically necessary dislocations (GNDs). We observe dislocation pile-ups at a grain boundary, as the neighbour grain prohibits easy passage for dislocation transmission. This incompatibility results in local micro-plasticity within the slipping grain, near to where the slip planes intersect the grain boundary, and we observe bands of GNDs lying near the grain boundary. We observe that the distribution of GNDs can be significantly influenced by the formation of grain boundary ledges that serve as secondary dislocation sources. This observation highlights the noncontinuum nature of polycrystal deformation and helps us understand the higher order complexity of grain boundary characteristics.Graphical Abstract:

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Section: Discussionmentioning

confidence: 99%

Dislocation density distribution at slip band-grain boundary intersections

et al. 2020

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“…Although it is difficult to capture the thermal strain/stress evolution during 3D printing, the residual deviatoric strain in this region can be quantified using the μXRD technique [15,42]. As shown in Fig.…”

Section: The Driving Force For Crack Initiation and Propagationmentioning

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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“…Numerous strategies have been developed to promote i‐motif formation at physiological pH, in order to assist in identifying ligands which can selectively interact with i‐motifs in vivo and determining the role of i‐motifs in transcription regulation and telomere biology . Recently pursued strategies include extending the length of the C‐tracts; altering the sugar, base, or phosphate moiety; utilizing branched RNA to hold the intercalated duplexes together; introducing the i‐motif forming sequence into a supercoiled DNA plasmid; and utilizing single‐walled carbon nanotubes, graphene quantum dots, or small molecule ligands . A wide range of modified sugars has been investigated, including RNA, arabinonucleic acid (ANA), locked (LNA) and unlocked (UNA) nucleic acids, 2′F‐RNA, and 2′‐deoxy‐2′‐fluoro‐arabinonucleic acids (2′F‐ANA) .…”

Section: Introductionmentioning

confidence: 99%

Probing Synergistic Effects of DNA Methylation and 2′‐β‐Fluorination on i‐Motif Stability

Assi

Lin

Serrano

et al. 2017

Chemistry A European J

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The possible role of DNA i‐motif structures in telomere biology and in the transcriptional regulation of oncogene promoter regions is supported by several recent studies. Herein we investigate the effect of four cytidine nucleosides (and combinations thereof) on i‐motif structure and stability, namely 2′‐deoxycytidine (dC), 2′‐deoxy‐5‐methyl‐cytidine (5‐Me‐dC), 2′‐deoxy‐2′‐fluoro‐arabinocytidine (2′F‐araC), and 2′‐deoxy‐2′‐fluoro‐5‐methyl‐arabinocytidine (5‐Me‐2′F‐araC). The base pair 5‐Me‐2′F‐araC:2′F‐araC produced i‐motifs with a pH1/2 (“pKa”) value that closely matches physiological pH (7.34±0.3). NMR analysis of the most stable telomeric sequence (HJ‐2) at pH 7.0 indicated that the structure is stabilized by hybrid 5‐Me‐dC:2′F‐araC hemiprotonated base pairs and therefore highlights the significance of the interplay between base and sugar modifications on the stability of i‐motif structures.

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Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

Cited by 61 publications

References 28 publications

Dislocation density distribution at slip band-grain boundary intersections

Dislocation density distribution at slip band-grain boundary intersections

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

Probing Synergistic Effects of DNA Methylation and 2′‐β‐Fluorination on i‐Motif Stability

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