〈a〉 Prismatic, 〈a〉 basal, and 〈c+a〉 slip strengths of commercially pure Zr by micro-cantilever tests

Gong, Jicheng; Britton, T. Ben; Cuddihy, Mitchell; Dunne, Fionn P.E.; Wilkinson, Angus J.

doi:10.1016/j.actamat.2015.06.020

Cited by 153 publications

(50 citation statements)

References 42 publications

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“…Therefore, by considering a prismatic slip system as the main deformation mechanism in α-Zr layers ( = 0.15 GPa) [84], = 0.075 GPa and = 0.42 GPa, a = 2 GPa is calculated, which matches reasonably well the measured strength.…”

supporting

confidence: 59%

“…7a). Gong et al [84] investigated the strength of different slip systems in single crystal pure α-Zr by microcantilever bending tests. Prismatic slip was found to be the most easy slip system with a critical resolved shear stress (CRSS) of ~ 153 MPa.…”

Section: Deformed Structuresmentioning

confidence: 99%

“…532 MPa were reported [84], respectively. In our study, the change in strength originating from the crystallographic rotation experienced by α-Zr is taken into account as follows:…”

mentioning

confidence: 99%

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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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supporting

confidence: 59%

Section: Deformed Structuresmentioning

confidence: 99%

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

Callisti

Polcar

2017

Acta Materialia

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“…Current approaches include using a final low current milling step404142, low energy ion milling4344 or flash polishing45 in order to “clean” FIB-damaged surfaces. The techniques presented here enable 3D measurements of the complex strain fields caused by FIB-milling and would as such allow a detailed assessment of the effectiveness of these approaches.…”

Section: Discussionmentioning

confidence: 99%

3D lattice distortions and defect structures in ion-implanted nano-crystals

Hofmann

Tarleton

Harder

et al. 2017

Sci Rep

117

138

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Focussed Ion Beam (FIB) milling is a mainstay of nano-scale machining. By manipulating a tightly focussed beam of energetic ions, often gallium (Ga+), FIB can sculpt nanostructures via localised sputtering. This ability to cut solid matter on the nano-scale revolutionised sample preparation across the life, earth and materials sciences. Despite its widespread usage, detailed understanding of the FIB-induced structural damage, intrinsic to the technique, remains elusive. Here we examine the defects caused by FIB in initially pristine objects. Using Bragg Coherent X-ray Diffraction Imaging (BCDI), we are able to spatially-resolve the full lattice strain tensor in FIB-milled gold nano-crystals. We find that every use of FIB causes large lattice distortions. Even very low ion doses, typical of FIB imaging and previously thought negligible, have a dramatic effect. Our results are consistent with a damage microstructure dominated by vacancies, highlighting the importance of free-surfaces in determining which defects are retained. At larger ion fluences, used during FIB-milling, we observe an extended dislocation network that causes stresses far beyond the bulk tensile strength of gold. These observations provide new fundamental insight into the nature of the damage created and the defects that lead to a surprisingly inhomogeneous morphology.

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“…Finally, the prefactors q g b i 2 m capture the density of glissile dislocations q g , their Burgers vector b i , and the dislocation jump frequency m. Many of the required properties are now directly measurable through the use of micromechanical tests. 24 Mechanical testing was performed on single-crystal CMSX4, oligocrystal MAR-002, and powder metallurgy FGH96 and RR1000 Ni-based superalloys under three-point bend testing, which focuses the maximum tensile stress at a known location for HR-DIC and HR-EBSD analyses.…”

Section: Characterization Modeling and Test Methodsmentioning

confidence: 99%

Toward Predictive Understanding of Fatigue Crack Nucleation in Ni-Based Superalloys

Jiang

Dunne

Britton

2017

JOM

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Predicting when and where materials fail is a holy grail for structural materials engineering. Development of a predictive capability in this domain will optimize the employment of existing materials, as well as rapidly enhance the uptake of new materials, especially in high-risk, high-value applications, such as aeroengines. In this article, we review and outline recent efforts within our research groups that focus on utilizing full-field measurement and calculation of micromechanical deformation in Ni-based superalloys. In paticular, we employ high spatial resolution digital image correlation (HR-DIC) to measure surface strains and a high-angular resolution electron backscatter diffraction technique (HR-EBSD) to measure elastic distortion, and we combine these with crystal plasticity finite element (CPFE) modeling. We target our studies within a system of samples that includes single, oligo, and polycrystals where the boundary conditions, microstructure, and loading configuration are precisely controlled. Coupling of experiment and simulation in this manner enables enhanced understanding of crystal plasticity, as demonstrated with case studies in deformation compatibility; spatial distributions of slip evolution; deformation patterning around microstructural defects; and ultimately development of predictive capability that probes the location of microstructurally sensitive fatigue cracks. We believe that these studies present a careful calibration and validation of our experimental and simulation-based approaches and pave the way toward new understanding of crack formation in engineering alloys.

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〈a〉 Prismatic, 〈a〉 basal, and 〈c+a〉 slip strengths of commercially pure Zr by micro-cantilever tests

Cited by 153 publications

References 42 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

3D lattice distortions and defect structures in ion-implanted nano-crystals

Toward Predictive Understanding of Fatigue Crack Nucleation in Ni-Based Superalloys

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