Stress measurements in nanocrystalline Ni electrodeposits

El-Sherik, A.M.; Shirokoff, John; Erb, U.

doi:10.1016/j.jallcom.2004.08.010

Cited by 67 publications

(28 citation statements)

References 18 publications

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“…Grain refinement through control of bath chemistry, pH and current density makes thick films more difficult to achieve since those settings must not deviate too far from ideal conditions during bath depletion. Despite some challenges, electrodeposited films with NC grain structure have been reported with thicknesses on the order of 100 µm [74,80] and even 1 mm [60].…”

Section: Deposition Techniquesmentioning

confidence: 99%

“…Comparison shows that internal residual stresses in NC Ni electrodeposits can be as large as (−)800 MPa compared to (−)140 MPa in MC Ni [80], although common levels are around (+)150 MPa [81]. Many plated films may also develop through-thickness stress gradients during deposition, as detected by wafer curvature measurements during deposition.…”

Section: Deposition Techniquesmentioning

confidence: 99%

“…These features complicate the interpretation of improved fatigue properties. Table 1 lists a summary [16,34,80,[106][107][108][109][110][111] of some processing-associated properties for the fabrication methods discussed in the previous section.…”

Section: Severe Plastic Deformation Processingmentioning

confidence: 99%

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A Review of Fatigue Behavior in Nanocrystalline Metals

2009

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Nanocrystalline metals have been shown to exhibit unique mechanical behavior, including break-down in Hall-Petch behavior, suppression of dislocation-mediated plasticity, induction of grain boundary sliding, and induction of mechanical grain coarsening. Early research on the fatigue behavior of nanocrystalline metals shows evidence of improved fatigue resistance compared to traditional microcrystalline metals. In this review, experimental and modeling observations are used to evaluate aspects of cyclic plasticity, microstructural stability, crack initiation processes, and crack propagation processes. In cyclic plasticity studies to date, nanocrystalline metals have exhibited strongly rate-dependent cyclic hardening, suggesting the importance of diffusive deformation mechanisms such as grain-boundary sliding. The cyclic deformation processes have also been shown to cause substantial mechanicallyinduced grain coarsening reminiscent of coarsening observed during large-strain monotonic deformation of nanocrystalline metals. The crack-initiation process in nanocrystalline metals has been associated with both subsurface internal defects and surface extrusions, although it is unclear how these extrusions form when the grain size is below the scale necessary for persistent slip band formation. Finally, as expected, nanocrystalline metals have very little resistance to crack propagation due to limited plasticity and the lack of crack path tortuosity among other factors. Nevertheless, like bulk metallic glasses, nanocrystalline metals exhibit both ductile fatigue striations and metal-like Paris-law behavior. The review provides both a comprehensive critical survey of existing literature and a summary of key areas for further investigation.

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Section: Deposition Techniquesmentioning

confidence: 99%

Section: Deposition Techniquesmentioning

confidence: 99%

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A Review of Fatigue Behavior in Nanocrystalline Metals

2009

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“…Furthermore, it should be noted that residual compressive stresses (~100 MPa) have been reported in electrodeposited nanostructured materials. [40] When they superpose on the crack-tip tensile stresses, they may result in premature crack face contact and the reduction of the effective crack-tip stress-intensity factor.…”

Section: A R-curve/fracture Behaviormentioning

confidence: 99%

Fatigue and Fracture of a Bulk Nanocrystalline NiFe Alloy

Yang

Imasogie

Fan

et al. 2008

Metall Mater Trans A

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This article presents the results of an experimental study of fracture and fatigue in a nanostructured (an average grain size of~23 nm) bulk Ni-18 wt pct Fe alloy that was produced using a pulsed electrodeposition technique. The fracture behavior of the alloy is investigated using fracture resistance experiments, while the fatigue behavior is studied in fatigue crack growth experiments. The alloy exhibits limited toughening as the crack initiates at a fracture toughness of about 25 MPa ffiffiffiffi m p and propagates with a slight increase to a plateau value of about 30 MPa ffiffiffiffi m p. The limited toughening arises from the slight increase in the crack-tip plasticdeformation zone at the early crack growth and ligament bridging due to the microcrack formation ahead of the tip of the main crack. In contrast with a flat fatigue-crack wake, a wavy crack wake was observed under monotonic loading. This trend is attributed to the following: (a) nanovoid coalescence at grain boundaries, (b) microcrack formation by joining nanovoids, and (c) the linking of microcracks with the main crack through the fracture of inclined bridging ligaments. The fractured surface is shown to contain ductile dimple structures with average diameters of~100 nm. Focused-ion-beam (FIB) methods are also used to study fatigue-crack growth. These results show that fatigue crack growth occurs by the coalescence of nanovoids that form ahead of the crack tip. The observed mechanisms of fatigue crack growth are shown to be consistent with the results of prior atomistic simulations.

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“…This is generically consistent with experimental measurements of very inhomogeneous stress in ED NC Ni. [23] Overall, the best fitting parameters are summarized in Table III and include modest adjustments to the analytic estimates from steps 1 through 4, obtained by iteration based on repeated QCP simulations.…”

Section: Application To Ed Nc Ni (30 Nm)mentioning

confidence: 99%

Critical Strengths for Slip Events in Nanocrystalline Metals: Predictions of Quantized Crystal Plasticity Simulations

Lee

Anderson

2010

Metall Mater Trans A

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This article studies how the monotonic and cyclic stress-strain response of nanocrystalline (NC) metals is affected by the grain-to-grain distribution of critical strengths (s c ) for slip events, as well as plastic predeformation (e pre p ). This is accomplished via finite element simulations that capture large jumps in plastic strain from dislocation slip events-a process referred to as quantized crystal plasticity (QCP). [1] The QCP simulations show that s c and e pre p significantly alter the monotonic and cyclic response at small strain, but only s c affects the response at large strain. These features are exploited to systematically infer the s c and e pre p characteristics that best fit experimental data for electrodeposited (ED) NC Ni. Key outcomes are the following:(1) the s c distribution is truncated, with an abrupt onset of slip events at a critical stress;(2) e pre p = À0.4 pct, signifying precompression; (3) there is reverse slip bias, meaning that reverse slip events are easier than forward events; and (4) highly inhomogeneous residual stress states can be enhanced or reduced by tensile deformation, depending on e pre p .

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Stress measurements in nanocrystalline Ni electrodeposits

Cited by 67 publications

References 18 publications

A Review of Fatigue Behavior in Nanocrystalline Metals

A Review of Fatigue Behavior in Nanocrystalline Metals

Fatigue and Fracture of a Bulk Nanocrystalline NiFe Alloy

Critical Strengths for Slip Events in Nanocrystalline Metals: Predictions of Quantized Crystal Plasticity Simulations

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