Stepwise work hardening induced by individual grain boundary in Cu bicrystal micropillars

Li, L. L.; Zhang, Z. J.; Tan, Jun; Jiang, Cheng; Qu, R.T.; Zhang, P.; Yang, Jun; Zhang, Z. F.

doi:10.1038/srep15631

Cited by 13 publications

(3 citation statements)

References 43 publications

(74 reference statements)

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“…For the first FIB milling step a Ga ion energy of 30 keV and beam current of 28 pA were used. These conditions closely match those used for the final milling cut during the manufacture of micro--mechanics test specimens [24,[51][52][53]. FIB milling was carried out in an incremental trench--milling mode with a target fluence of 0.65 nC/μm 2 (4.06 x 10 9 ions/ μm 2 ) to achieve a glancing--incidence milling condition.…”

Section: Focussed Ion Beam Millingmentioning

confidence: 99%

Glancing-incidence focussed ion beam milling: A coherent X-ray diffraction study of 3D nano-scale lattice strains and crystal defects

Hofmann¹,

Harder²,

Liu³

et al. 2018

Acta Materialia

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This study presents a detailed examination of the lattice distortions introduced by glancing incidence Focussed Ion Beam (FIB) milling. Using non--destructive multi--reflection Bragg coherent X--ray diffraction we probe damage formation in an initially pristine gold micro-crystal following several stages of FIB milling. These experiments allow access to the full lattice strain tensor in the micro--crystal with 25 nm 3D spatial resolution, enabling a nano-scale analysis of residual lattice strains and defects formed. Our results show that 30 keV glancing incidence milling produces fewer large defects than normal incidence milling at the same energy. However the resulting residual lattice strains have similar magnitude and extend up to 50 nm into the sample. At the edges of the milled surface, where the ion-beam tails impact the sample at near--normal incidence, large dislocation loops with a range of burgers vectors are formed. Further glancing incidence FIB polishing with 5 keV ion energy removes these dislocation loops and reduces the lattice strains caused by higher energy FIB milling. However, even at the lower ion energy, damage--induced lattice strains are present within a 20 nm thick surface layer. These results highlight the need for careful consideration and management of FIB damage. They also show that low--energy FIB--milling is an effective tool for removing FIB--milling induced lattice strains. This is important for the preparation of micro--mechanical test specimens and strain microscopy samples.

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Section: Focussed Ion Beam Millingmentioning

confidence: 99%

Glancing-incidence focussed ion beam milling: A coherent X-ray diffraction study of 3D nano-scale lattice strains and crystal defects

Hofmann¹,

Harder²,

Liu³

et al. 2018

Acta Materialia

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“…The conclusions can be divided into two categories. The first believes the dislocations can be blocked effectively by GBs in the form of pile-ups [12,57,58], which leads to a significant rise in the hardening rate as well as much smoother stress-strain response with lower strain bursts than that observed in the SCPs [14]. However, the second supposes that the dislocations can be absorbed by the GBs, and no pile-ups against the GBs can be formed, which renders a lower hardening rate and higher strain bursts than that observed in the SCPs [13,15,51], completely opposing the finding of the above case.…”

Section: Application To Compression Of Single-and Bi-crystal Micropil...mentioning

confidence: 99%

An extended 3D discrete-continuous model and its application on single- and bi-crystal micropillars

Huang

Liang

2017

Modelling Simul. Mater. Sci. Eng.

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A 3D discrete-continuous model (3D DCM), which couples the 3D discrete dislocation dynamics (3D DDD) and finite element method (FEM), is extended in this study. New schemes for two key information transfers between DDD and FEM, i.e. plastic-strain distribution from DDD to FEM and stress transfer from FEM to DDD, are suggested. The plastic strain induced by moving dislocation segments is distributed to an elementary spheroid (ellipsoid or sphere) via a specific new distribution function. The influence of various interfaces (such as free surfaces and grain boundaries (GBs)) on the plastic-strain distribution is specially considered. By these treatments, the deformation fields can be solved accurately even for dislocations on slip planes severely inclined to the FE mesh, with no spurious stress concentration points produced. In addition, a stress correction by singular and non-singular theoretical solutions within a cut-off sphere is introduced to calculate the stress on the dislocations accurately. By these schemes, the present DCM becomes less sensitive to the FE mesh and more numerically efficient, which can also consider the interaction between neighboring dislocations appropriately even though they reside in the same FE mesh. Furthermore, the present DCM has been employed to model the compression of single-crystal and bi-crystal micropillars with rigid and dislocation-absorbed GBs. The influence of internal GB on the jerky stress-strain response and deformation mode is studied in detail to shed more light on these important micro-plastic problems.

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“…Moving up the chain of complexity, the literature on bicrystals and twinned crystals exemplifies the continuation of classic early experiments (47)(48)(49) but at much higher resolution and as a function of small size. These experiments have revealed detwinning in magnesium (50) at a stress plateau that restores the twin to the parent orientation but leaves behind dislocation debris that, in turn, leads to work hardening after a single crystal is created, greater homogeneity of slip caused by even a single grain boundary (51), greater homogeneity of slip and reduced strain bursts compared with single crystals, and both twin strengthening and deformation by detwinning (52,53). Strain rate effects in silver nanowires with a single high-angle grain boundary running the length of the sample (54) revealed, interestingly, that low strain rates led to random dislocation emission at quasistatic stresses from the surface, causing slip localization and failure due to rapid necking at low strains.…”

Section: Introductionmentioning

confidence: 99%

Small-Scale Mechanical Testing

Jayaram

2022

Annu. Rev. Mater. Res.

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This article reviews recent developments in small-scale mechanical property testing with some emphasis on intermediate (meso) length scales in complex microstructures and coated systems. The introduction summarizes size effects discovered from a century ago up to the recent explosion in micropillar testing that established many length scale effects in yielding and fracture. The bulk of the article deals with plasticity and fracture in polyphasic and microstructurally graded systems, including biomaterials, composites, and thermal protection systems, highlighting the use of in situ methods where mechanical tests are coupled to synchrotron X-ray scattering, electron backscattering, radiation damage, and digital image correlation. Expected final online publication date for the Annual Review of Materials Research, Volume 52 is July 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Stepwise work hardening induced by individual grain boundary in Cu bicrystal micropillars

Cited by 13 publications

References 43 publications

Glancing-incidence focussed ion beam milling: A coherent X-ray diffraction study of 3D nano-scale lattice strains and crystal defects

Glancing-incidence focussed ion beam milling: A coherent X-ray diffraction study of 3D nano-scale lattice strains and crystal defects

An extended 3D discrete-continuous model and its application on single- and bi-crystal micropillars

Small-Scale Mechanical Testing

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