Crack initiation at twin boundaries due to slip system mismatch

Knorr, Alain Franz; Marx, Michael; Schaefer, Florian

doi:10.1016/j.scriptamat.2014.09.015

Cited by 21 publications

(3 citation statements)

References 17 publications

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“…Representative subsurface cracks with their ND-IPF maps are shown in Fig.8(b)-(e). In accordance with previous studies[37,48,49],TBs show great resistance to crack propagation. An intergranular crack is deflected and a transgranular crack becomes blunted when they reach TBs as shown in Fig.8(c).…”

supporting

confidence: 92%

“…Other GBs allows partial or full transmission of dislocations depending on the deformation behavior of adjacent grains and the character of GBs. By considering this, the concept of slip transferability and its impact on crack initiation along GBs was brought up to analyze the fatigue crack initiation and growth [37,38]. And 3D characterization of the GB makes it possible to analyze the incompatibility stresses and reveal the transmission of the plasticity across the GB.…”

Section: Introductionmentioning

confidence: 99%

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Effect of electrochemical charging on the hydrogen embrittlement susceptibility of alloy 718

Wang

Wan

et al. 2019

Acta Materialia

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The susceptibility of age-hardened nickel-based 718 superalloy to hydrogen embrittlement was studied by the controlled electrochemical charging combined with slow strain-rate tensile tests (SSRT) and advanced characterization techniques. We proposed some novel ideas of explaining hydrogen embrittlement mechanisms of the studied material in regard to two cracking morphologies: transgranular and intergranular cracking. It is for the first time to report that electrochemical charging alone could cause slip lines, surface and subsurface cracks on nickel-based superalloys. The formation of pre-damages was discussed by calculating the hydrogen concentration gradient generated during cathodic charging. Predamages were proved to result in transgranular cracks and lead to the evident reduction of mechanical properties. In addition, the STRONG (Slip Transfer Resistance of *Manuscript_clean Click here to download Manuscript: Revised Manuscript_clean_A-19-1789_R1.docx Click here to view linked References Neighbouring Grains) model was used to analyze the dependence of hydrogen-assisted intergranular cracking on the microscopic incompatibility of the grain boundaries. The results show that in the presence of hydrogen, grain boundaries with a lower dislocation slip transmission are more prone to cracking during loading and vice versa.

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supporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of alloy 718

Wang

Wan

et al. 2019

Acta Materialia

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“…The critical transmission stress is generally studied based on image force on dislocations due to the moduli mismatch [20][21][22][23][24]. Furthermore, the interaction between dislocations and special boundaries like twin boundaries has been investigated by many researchers [25][26][27][28]. As discussed above, it is believed that a critical stress is needed for the dislocation to get from one grain to the other grain across the GB.…”

Section: Introductionmentioning

confidence: 99%

Atomic Force Microscopy Study of Discrete Dislocation Pile-ups at Grain Boundaries in Bi-Crystalline Micro-Pillars

2020

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Compression tests at low strains were performed to theoretically analyze the effects of anisotropic elasticity, misorientation, grain boundary (GB) stiffness, interfacial dislocations, free surfaces, and critical force on dislocation pile-ups in micro-sized Face-Centered Cubic (FCC) Nickel (Ni) and α -Brass bi-crystals. The spatial variations of slip heights due to localized slip bands terminating at GB were measured by Atomic Force Microscopy (AFM) to determine the Burgers vector distributions in the dislocation pile-ups. These distributions were then simulated by discrete pile-up micromechanical calculations in anisotropic bi-crystals consistent with the experimentally measured material parameters. The computations were based on the image decomposition method considering the effects of interphase GB and free surfaces in multilayered materials. For Ni and α -Brass, it was found that the best predicted step height spatial profiles were obtained considering anisotropic elasticity, free surface effects, a homogeneous external stress and a certain critical force in the material to equilibrate the dislocation pile-ups.

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The finding of anisotropic compatibility of grain boundaries in a directionally solidified superalloy

Tan,

Zhang,

Gao

et al. 2024

J Mater Sci

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The anisotropic compatibility of grain boundaries (GBs) is found in a directionally solidified superalloy, when loading is aligned with (L sample) or transverse (T sample) to the grain growth direction. The greater compatibility of GBs is shown in the L sample by calculating the parameter m′ of the GBs using two developed models. The first model considers the theoretical scenario that grains grow along the perfect [001] orientation, and the compatibility between the neighbouring grains with all kinds of orientation difference is calculated. The second model, termed as Schmid-factor-tolerance model, considers the effects of asymmetrical slip systems caused by the deviation of grain growth direction from the [001] orientation in a real microstructure. Validation of the model is achieved through fatigue tests, demonstrating its capability to interpret and predict the crack initiation behaviours at grain boundaries. Combined with the fatigue tests to illustrate the anisotropic fracture behaviours of the L and T specimens, it shows that the intergranular cracks are more likely to occur in the T specimen with poor compatibility, which proves the capability of predicting the intergranular cracks for the Schmid-factor-tolerance model.

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Crack initiation at twin boundaries due to slip system mismatch

Cited by 21 publications

References 17 publications

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of alloy 718

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of alloy 718

Atomic Force Microscopy Study of Discrete Dislocation Pile-ups at Grain Boundaries in Bi-Crystalline Micro-Pillars

The finding of anisotropic compatibility of grain boundaries in a directionally solidified superalloy

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