Micron-Scale Deformation: A Coupled <i>In Situ</i> Study of Strain Bursts and Acoustic Emission

Hegyi, Ádám István; Ispánovity, Péter Dusán; Knapek, Michal; Tüzes, Dániel; Máthis, Krisztián; Chmelı́k, František; Dankházi, Zoltán; Varga, Gábor; Groma, István

doi:10.1017/s1431927617012594

Cited by 22 publications

(14 citation statements)

References 43 publications

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“…Room temperature compression tests on the micropillars were carried out in high vacuum mode inside the SEM chamber to allow in situ monitoring of the deformation process and slip activity on the pillars' surface by secondary and backscattered electrons. A custom-made nanoindenter 34,35 shown in Extended Data Fig. 1 was used without any load or strain feedback loop integrated.…”

Section: Testing Devicementioning

confidence: 99%

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Dislocation Avalanches: Earthquakes on the Micron Scale

Ispánovity¹,

Ugi²,

Péterffy³

et al. 2021

Preprint

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Metals usually deform irreversibly as a result of the motion of dislocations that are line-like defects in the crystal lattice. Compression experiments of micron-scale specimens 1, 2 as well as acoustic emission (AE) measurements performed on bulk samples 3, 4 revealed that the motion of dislocations resembles a stick-slip process. As a result, deformation proceeds in a series of unpredictable local strain bursts with a scale-free size distribution 5, 6 . Here we use a unique, highly sensitive experimental set-up, which allows us to detect the weak AE waves of dislocation slip during the compression of micron-sized Zn pillars. This opens up new vistas for studying the stop-and-go dislocation motion in detail and understanding the physical origin of AE events. Profound correlation is observed between the size of the deformation events and the total energy of the emitted signals that, as we conclude, are induced by the collective dissipative motion of dislocations. We also show by statistical

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Section: Testing Devicementioning

confidence: 99%

“…The applied sampling rate was 200 Hz, while platen velocity (if not stated otherwise) and spring constant were 10 nm/s and 10 mN/µm, respectively. For a detailed description of the device, the reader is referred to 34 . Exemplary stress-strain curves are presented in Extended Data Fig.…”

Section: Testing Devicementioning

confidence: 99%

Dislocation Avalanches: Earthquakes on the Micron Scale

Ispánovity¹,

Ugi²,

Péterffy³

et al. 2021

Preprint

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“…These pillars can be considered as non-tapered (< 0.8 • ). After sample preparation, a custom-made nanoindenter [31] was used. Three pillars were compressed to 0.7%, 4.3% and 10% strains with a fixed crosshead velocity of 9 × 10 −3 µm/s.…”

Section: Sample Preparation and Experimental Realizationmentioning

confidence: 99%

Investigation of geometrically necessary dislocation structures in compressed Cu micropillars by 3-dimensional HR-EBSD

Kalácska

Dankházi

Zilahi

et al. 2020

Materials Science and Engineering: A

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Mechanical testing of micropillars is a field that involves new physics, as the behaviour of materials is non-deterministic at this scale. To better understand their deformation mechanisms we applied 3-dimensional high angular resolution electron backscatter diffraction (3D HR-EBSD) to reveal the dislocation distribution in deformed single crystal copper micropillars. Identical micropillars were fabricated by focused ion beam (FIB) and compressed at room temperature. The deformation process was stopped at different strain levels (≈ 1%, 4% and 10%) to study the evolution of geometrically necessary dislocations (GNDs). Serial slicing with FIB and consecutive HR-EBSD mapping on the (100) side was used to create and compare 3-dimensional maps of the deformed volumes. Average GND densities were calculated for each deformation step. Total dislocation density calculation based on X-ray synchrotron measurements were conducted on the 4% pillar to compare dislocation densities determined by the two complementary methods. Scanning transmission electronmicroscopy (STEM) and transmission electronmicroscopy (TEM) images were captured on the 10% pillar to visualize the actual dislocation structure. With the 3D HR-EBSD technique we have studied the geometrically necessary dislocations evolving during the deformation of micropillars. An intermediate behaviour was found at the studied sample size between bulk and nanoscale plasticity: A well-developed dislocation cell structure built up upon deformation but with significantly lower GND density than in bulk. This explains the simultaneous observation of strain hardening and size effect at this scale.

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“…In the present experiments, the maximum applied load was~15 mN. The technical details of the indenter device can be found in reference [27]. To ensure the reproducibility of the compression data, three micropillars were fabricated and compressed for each film.…”

Section: Micropillar Compression Testmentioning

confidence: 99%

Micropillar Compression Study on the Deformation Behavior of Electrodeposited Ni–Mo Films

et al. 2020

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The influence of Mo addition on the compression behavior of Ni films was studied by micropillar deformation tests. Thus, films with low (0.4 at.%) and high (5.3 at.%) Mo contents were processed by electrodeposition and tested by micropillar compression up to the plastic strain of about 0.26. The microstructures of the films before and after compression were studied by transmission electron microscopy. It was found that the as-deposited sample with high Mo concentration has a much lower grain size (~26 nm) than that for the layer with low Mo content (~240 nm). In addition, the density of lattice defects such as dislocations and twin faults was considerably higher for the specimen containing a larger amount of Mo. These differences resulted in a four-times higher yield strength for the latter sample. The Ni film with low Mo concentration showed a normal strain hardening while the sample having high Mo content exhibited a continuous softening after a short hardening period. The strain softening was attributed to detwinning during deformation.

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Micron-Scale Deformation: A Coupled In Situ Study of Strain Bursts and Acoustic Emission

Cited by 22 publications

References 43 publications

Dislocation Avalanches: Earthquakes on the Micron Scale

Dislocation Avalanches: Earthquakes on the Micron Scale

Investigation of geometrically necessary dislocation structures in compressed Cu micropillars by 3-dimensional HR-EBSD

Micropillar Compression Study on the Deformation Behavior of Electrodeposited Ni–Mo Films

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