Deformation of electrodeposited nanocrystalline nickel

Kumar, K. Kishore; Suresh, S.; Chisholm, M. F.; Horton, J.A.; Wang, P.

doi:10.1016/s1359-6454(02)00421-4

Cited by 714 publications

(380 citation statements)

References 37 publications

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“…Furthermore, the trends in the elastic limit, the yield strength and the ultimate tensile strength in the range of almost eight decades of strain rate in Fig. 6a and b point to strain rate sensitivity, which is in agreement with the previous results for Au [3][4][5][6][7]19] and other nanocrystalline fcc materials, such as Cu [15] and Ni [15]. In particular, the elastic limit increased by 86% and 126% from the slowest (10 À6 s À1 ) to the fastest (20 s À1 ) loading rate for 0.85 and 1.76 lm thick specimens, respectively, whereas the 0.2% yield strength increased by 47% and 38%, respectively.…”

Section: Rate-dependent Mechanical Behavior Of Au Filmssupporting

confidence: 92%

“…The significant contribution of room temperature creep to the mechanics of the present films is possible due to the large elastic stresses that are attainable in the material because of the lack of large defects to initiate localization and, more importantly, the small grain size that supports a strong Hall-Petch effect. Therefore, at the high stresses (450-700 MPa) at which the Au films reached their elastic limit at 10 À4 -20 s À1 , it is expected that intragranular dislocation plasticity [4,36] dominates, while at the slower strain rates, 10 À6 -10 À4 s À1 , grain boundary diffusion and dislocation nucleation and pinning processes play a major role in inelastic deformation, as supported by the marked change in the rate sensitivity factor at 10 À4 s À1 .…”

Section: Strain Rate Sensitivity Of Nanocrystalline Au Filmsmentioning

confidence: 98%

“…However, the beneficial effect of nanocrystallinity is weighed by the increased strain rate sensitivity [2][3][4][5][6][7] and increased creep rates compared to films with larger grain size. Nanocrystalline metals allow for large material volumes occupied by grain boundaries that control dislocation nucleation [4,8] and grain boundary mediated creep [9] while affecting the relative contribution of thermal and stress driven inelastic processes [10][11][12]. These often competing mechanisms result in increased rate sensitivity which is not uniform across time scales: diffusion controlled processes are important at slow loading rates and may dominate in materials with large percentage of grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

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Strain rate sensitivity of nanocrystalline Au films at room temperature

et al. 2010

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Dimitrios, "Strain rate sensitivity of nanocrystalline Au films at room temperature" (2010) AbstractThe effect of strain rate on the inelastic properties of nanocrystalline Au films was quantified with 0.85 and 1.76 lm free-standing microscale tension specimens tested over eight decades of strain rate, between 6 Â 10 À6 and 20 s À1 . The elastic modulus was independent of the strain rate, 66 ± 4.5 GPa, but the inelastic mechanical response was clearly rate sensitive. The yield strength and the ultimate tensile strength increased with the strain rate in the ranges 575-895 MPa and 675-940 MPa, respectively, with the yield strength reaching the tensile strength at strain rates faster than 10 À1 s À1 . The activation volumes for the two film thicknesses were 4.5 and 8.1 b 3 , at strain rates smaller than 10 À4 s À1 and 12.5 and 14.6 b 3 at strain rates higher than 10 À4 s À1 , while the strain rate sensitivity factor and the ultimate tensile strain increased below 10 À4 s À1 . The latter trends indicated that the strain rate regime 10 À5 -10 À4 s À1 is pivotal in the mechanical response of the particular nanocrystalline Au films. The increased rate sensitivity and the reduced activation volume at slow strain rates were attributed to grain boundary processes that also led to prolonged (5-6 h) and significant primary creep with initial strain rate of the order of 10 À7 s À1 .

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Section: Rate-dependent Mechanical Behavior Of Au Filmssupporting

confidence: 92%

Section: Strain Rate Sensitivity Of Nanocrystalline Au Filmsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Strain rate sensitivity of nanocrystalline Au films at room temperature

et al. 2010

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“…Some experimental investigations [13][14][15][16] indicate that grain boundary sliding is the prevailing mechanism of deformation for nc and ufg materials. Hugo et al [17] and Kumar et al [18] performed in situ tensile tests in a transmission electron microscope. Their observations reveal that dislocationmediated plasticity plays a dominant role in the deformation of nc Ni.…”

mentioning

confidence: 99%

Shear bands at the fatigue crack tip of nanocrystalline nickel

Xie

Hong

2007

Scripta Materialia

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Fatigue crack growth rates in electrodeposited nanocrystalline Ni and its coarse counterpart were experimentally investigated in this paper. The shear bands, called the epsilon plastic zone, were observed on the surface of nanocrystalline Ni samples. The length of the shear bands is close to the estimated size of the plastic zone at the crack tip. Atomic force microscopy measurements indicate that the shear strain in the shear bands and the width of shear bands increase with related crack length.

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“…Intergranular fracture is the governing process for mechanical failure in nanocrystalline metals [1]. Intergranular crack propagation is strongly influenced by the specifics of the grain boundary (GB) interface, the structure of which still poses many unresolved issues [2].…”

Section: Introductionmentioning

confidence: 99%

Dynamics of nanoscale grain-boundary decohesion in aluminum by molecular-dynamics simulation

et al. 2007

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The dynamics and energetics of intergranular crack growth along a flat grain boundary in aluminum is studied by a molecular-dynamics simulation model for crack propagation under steady-state conditions. Using the ability of the molecular-dynamics simulation to identify atoms involved in different atomistic mechanisms, it was possible to identify the energy contribution of different processes taking place during crack growth. The energy contributions were divided as: elastic energy -defined as the potential energy of the atoms in fcc crystallographic state; and plastically stored energy -the energy of stacking faults and twin boundaries; grain-boundary and surface energy. In addition, monitoring the amount of heat exchange with the moleculardynamics thermostat gives the energy dissipated as heat in the system. The energetic analysis indicates that the majority of energy in a fast growing crack is dissipated as heat. This dissipation increases linearly at low speed, and faster than linear at speeds approaching 1/3 the Rayleigh wave speed when the crack tip becomes dynamically unstable producing periodic dislocation bursts until the crack is blunted.

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Deformation of electrodeposited nanocrystalline nickel

Cited by 714 publications

References 37 publications

Strain rate sensitivity of nanocrystalline Au films at room temperature

Strain rate sensitivity of nanocrystalline Au films at room temperature

Shear bands at the fatigue crack tip of nanocrystalline nickel

Dynamics of nanoscale grain-boundary decohesion in aluminum by molecular-dynamics simulation

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