Strain rate sensitivity of nanolayered Cu/X (X=Cr, Zr) micropillars: Effects of heterophase interface/twin boundary

Zhang, J.Y.; Wang, Y.Q.; Wu, Kai; Zhang, P.; Liu, G.; Zhang, G.J.; Sun, Jun

doi:10.1016/j.msea.2014.06.025

Cited by 21 publications

(6 citation statements)

References 103 publications

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“…6a) NMMs in relation to hCu/L [48]. The activation volume decreases from ~ 9.4b 3 to ~ 3b 3 for larger hNb/L, as also reported for Cu/Zr NMMs for similar length scales [73], although an exception is found for the film with hNb = 11 nm (or L = 27 nm). It indicates that in this particular case, the relative amount of Nb is not the only factor affecting V * .…”

Section: Indentation Creepsupporting

confidence: 79%

Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers

Callisti

Polcar

2017

Acta Materialia

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A combination of transmission electron microscopy analyses and nanomechanical measurements was performed in this study to reveal deformation and strengthening mechanisms occurring in sputtered Zr/Nb nanoscale metallic multilayers (NMMs) with a periodicity (L) in the range 6 -167 nm. Electron diffraction analyses revealed a change in the crystallographic orientation of α-Zr when L ≤ 27 nm, while Nb structure retained the same orientations regardless of L. For L > 60 nm, the strengthening mechanism is well described by the Hall-Petch model, while for 27 < L < 60 nm the refined CLS model comes into picture. A decrease in strength is found for L < 27 nm, which could not be simply explained by considering only misfit and Koehler stresses. For L ≤ 27 nm, plastic strain measured across compressed NMMs revealed a change in the plastic behaviour of α-Zr, which experienced a hard-to-soft transition. At these length scales, the combination of two structural factors were found to affect the strength. These relate to the formation of weaker interfaces which extend the effective distance between strong barriers against dislocation transmission, thus producing a softening effect. 1The second effect relates to the crystallographic orientation change exhibited by α-Zr for L < 27 nm with a consequent change of the dominant slip system. The actual strength at these smaller length scales was effectively quantified by taking these structural aspects into account in the interface barrier strength model.

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Section: Indentation Creepsupporting

confidence: 79%

Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers

Callisti

Polcar

2017

Acta Materialia

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“…Nanoscale metallic multilayers have been studied in detail in the last 10 years due to their outstanding mechanical properties [1][2][3][4], especially for individual layer thickness below ≈100 nm, that originate from the high density of interfaces, that block dislocation transmission. From all possible metal combinations, fcc/bcc systems with incoherent interfaces, like Cu/Nb, have been widely studied, as they can achieve high strength at ambient temperature [1,5].…”

Section: Introductionmentioning

confidence: 99%

Selective oxidation-induced strengthening of Zr/Nb nanoscale multilayers

et al. 2017

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The paper presents a new approach, based on controlled oxidation of nanoscale metallic multilayers, to produce strong and hard oxide/metal nanocomposite coatings with high strength and good thermal stability. The approach is demonstrated by performing long term annealing on sputtered Zr/Nb nanoscale metallic multilayers and investigating the evolution of their microstructure and mechanical properties by combining analytical transmission electron microscopy, nano-mechanical tests and finite element models. Asdeposited multilayers were annealed at 350ºC in air for times ranging between 1 -336 hours. The elastic modulus increased by ~ 20% and the hardness by ~ 42% after 15 hours of annealing. Longer annealing times did not lead to changes in hardness, although the elastic modulus increased up to 35% after 336 hrs. The hcp Zr layers were rapidly transformed into monoclinic ZrO 2 (in the first 15 hours), while the Nb layers were progressively oxidised, from top surface down towards the substrate, to form an 2 amorphous oxide phase at a much lower rate. The sequential oxidation of Zr and Nb layers was key for the oxidation to take place without rupture of the multi-layered structure and without coating spallation, as the plastic deformation of the metallic Nb layers allowed for the partial relieve of the residual stresses developed as a result of the volumetric expansion of the Zr layers upon oxidation. Moreover, the development of residual stresses induced further changes in mechanical properties in relation to the annealing time, as revealed by finite element simulations.

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“…Therefore, utilizing the additional information gained from the images recorded during in situ testing can make a significant impact. While the classical DIC methods have been applied to micron sized specimens and allow for better strain resolution [37,38], it raises the need for higher-resolution imaging data and is therefore, not suitable for quasi-continuous testing, which is the pre-requisite for various mechanical testing methods due to occurrence of material dependent strain rate sensitive characteristics [39][40][41][42]. Furthermore, high plastic deformation has always been a challenge for classical DIC due the fact that the features could deform quite drastically and move a large distance, which is demanding for any greyscale histogram cross-correlation algorithm.…”

Section: Discussionmentioning

confidence: 99%

Extracting information from noisy data: strain mapping during dynamic in situ SEM experiments

Alfreider

Meindlhumer

Maier–Kiener

et al. 2021

Journal of Materials Research

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Micromechanical testing techniques can reveal a variety of characteristics in materials that are otherwise impossible to address. However, unlike to macroscopic testing, these miniaturized experiments are more challenging to realize and analyze, as loading and boundary conditions can often not be controlled to the same extent as in standardized macroscopic tests. Hence, exploiting all possible information from such an experiment seems utmost desirable. In the present work, we utilize dynamic in situ microtensile testing of a nanocrystalline equiatomic CoCrFeMnNi high entropy alloy in conjunction with initial feature tracking to obtain a continuous two-dimensional strain field. This enables an evaluation of true stress–strain data as well as of the Poisson’s ratio and allows to study localization of plastic deformation for the specimen. We demonstrate that the presented image correlation method allows for an additional gain of information in these sophisticated experiments over commercial tools and can serve as a starting point to study deformation states exhibiting more complex strain fields. Graphic abstract

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Strain rate sensitivity of nanolayered Cu/X (X=Cr, Zr) micropillars: Effects of heterophase interface/twin boundary

Cited by 21 publications

References 103 publications

Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers

Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers

Selective oxidation-induced strengthening of Zr/Nb nanoscale multilayers

Extracting information from noisy data: strain mapping during dynamic in situ SEM experiments

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