On strain hardening mechanism in gradient nanostructures

Li, Jianjun; Weng, George J.; Chen, Shaohua; Wu, Xiaolei

doi:10.1016/j.ijplas.2016.10.003

Cited by 229 publications

(51 citation statements)

References 60 publications

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“…The above-mentioned experimental evidences have shown that the enhanced mechanical properties (uniaxial tensile, dynamic and fatigue) can be achieved by the gradient structure, while the detailed mechanisms underlying the observed mechanical behaviors still need further investigations and how the mechanical properties can be optimized in the gradient structure need be clarified by theoretical and numerical modeling. In the past decade, several approaches (i.e., dislocation density-based continuum plasticity modeling [48,54,55], dislocation mechanism-based size-dependent crystal plasticity modeling [64], Crystal plasticity finite element modeling [65] and molecular dynamics (MD) simulation [60]) have been utilized to understand the strengthening and strain hardening behaviors. Li et al [48,54] have developed a dislocation density-based continuum plasticity model to reveal the extra strain hardening behaviors in the gradient structure of IF steel, in which the nonuniform deformation of the lateral surface, the interaction of different layers along the depth, GNDs and back stress were considered (Figure 11).…”

Section: Theoretical and Numerical Work For Gradient Structuresmentioning

confidence: 99%

“…In the past decade, several approaches (i.e., dislocation density-based continuum plasticity modeling [48,54,55], dislocation mechanism-based size-dependent crystal plasticity modeling [64], Crystal plasticity finite element modeling [65] and molecular dynamics (MD) simulation [60]) have been utilized to understand the strengthening and strain hardening behaviors. Li et al [48,54] have developed a dislocation density-based continuum plasticity model to reveal the extra strain hardening behaviors in the gradient structure of IF steel, in which the nonuniform deformation of the lateral surface, the interaction of different layers along the depth, GNDs and back stress were considered (Figure 11). A simple physical law with two dimensionless parameters has been established to build the correlation between the strong extra strain hardening and the nonuniform deformation of the lateral surface, and these two parameters can be determined by experimental data.…”

Section: Theoretical and Numerical Work For Gradient Structuresmentioning

confidence: 99%

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A Review on Heterogeneous Nanostructures: A Strategy for Superior Mechanical Properties in Metals

Yang

Yuan

et al. 2019

Metals

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Generally, strength and ductility are mutually exclusive in homogeneous metals. Nanostructured metals can have much higher strength when compared to their coarse-grained counterparts, while simple microstructure refinement to nanoscale generally results in poor strain hardening and limited ductility. In recent years, heterogeneous nanostructures in metals have been proven to be a new strategy to achieve unprecedented mechanical properties that are not accessible to their homogeneous counterparts. Here, we review recent advances in overcoming this strength–ductility trade-off by the designs of several heterogeneous nanostructures in metals: heterogeneous grain/lamellar/phase structures, gradient structure, nanotwinned structure and structure with nanoprecipitates. These structural heterogeneities can induce stress/strain partitioning between domains with dramatically different strengths, strain gradients and geometrically necessary dislocations near domain interfaces, and back-stress strengthening/hardening for high strength and large ductility. This review also provides the guideline for optimizing the mechanical properties in heterogeneous nanostructures by highlighting future challenges and opportunities.

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Section: Theoretical and Numerical Work For Gradient Structuresmentioning

confidence: 99%

Section: Theoretical and Numerical Work For Gradient Structuresmentioning

confidence: 99%

A Review on Heterogeneous Nanostructures: A Strategy for Superior Mechanical Properties in Metals

Yang

Yuan

et al. 2019

Metals

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“…These gradients render biological materials resistant against harsh mechanical loads such as those imposed by weather or predators. Recently, manmade gradient structures have also been shown to provide improved strength-ductility properties 27 , 29 – 31 , 35 – 47 , lower friction coefficients 48 , better fatigue resistance 49 – 51 , and exceptional stretchability 52 . The underlying artificial gradient structures that were utilized in these studies mainly included grain size gradients spanning over four orders of magnitude 53 or nanotwin gradients in twinning induced plasticity steel 54 .…”

Section: Introductionmentioning

confidence: 99%

Eliminating deformation incompatibility in composites by gradient nanolayer architectures

Gibson

et al. 2018

Sci Rep

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Composite materials usually possess a severe deformation incompatibility between the soft and hard phases. Here, we show how this incompatibility problem is overcome by a novel composite design. A gradient nanolayer-structured Cu-Zr material has been synthesized by magnetron sputtering and tested by micropillar compression. The interface spacing between the alternating Cu and Zr nanolayers increases gradually by one order of magnitude from 10 nm at the surface to 100 nm in the centre. The interface spacing gradient creates a mechanical gradient in the depth direction, which generates a deformation gradient during loading that accumulates a substantial amount of geometrically necessary dislocations. These dislocations render the component layers of originally high mechanical contrast compatible. As a result, we revealed a synergetic mechanical response in the material, which is characterized by fully compatible deformation between the constituent Cu and Zr nanolayers with different thicknesses, resulting in a maximum uniform layer strain of up to 60% in the composite. The deformed pillars have a smooth surface, validating the absence of deformation incompatibility between the layers. The joint deformation response is discussed in terms of a micromechanical finite element simulation.

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“…1 . Examples are nanotwinned Cu 10 , gradient Cu 11 , 12 , gradient IF steel 8 , 13 – 16 , gradient nano-twinned TWIP steel 17 , hierarchical nanotwinned steel 18 , hierarchical Al 19 , bimodal Cu 20 , bimodal lamella Ti 21 , multi-modal Ni 22 , and nano-grained Cu with amorphous interfaces 23 in which the intrinsic scale, e.g. the grain size, twin or interface thickness spans over several orders of magnitude either sharp or gradually.…”

Section: Introductionmentioning

confidence: 99%

Large strain synergetic material deformation enabled by hybrid nanolayer architectures

Zhang

et al. 2017

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Nanolayered metallic composites are much stronger than pure nanocrystalline metals due to their high density of hetero-interfaces. However, they are usually mechanically instable due to the deformation incompatibility among the soft and hard constituent layers promoting shear instability. Here we designed a hybrid material with a heterogeneous multi-nanolayer architecture. It consists of alternating 10 nm and 100 nm-thick Cu/Zr bilayers which deform compatibly in both stress and strain by utilizing the layers’ intrinsic strength, strain hardening and thickness, an effect referred to as synergetic deformation. Micropillar tests show that the 6.4 GPa-hard 10 nm Cu/Zr bilayers and the 3.3 GPa 100 nm Cu layers deform in a compatible fashion up to 50% strain. Shear instabilities are entirely suppressed. Synergetic strengthening of 768 MPa (83% increase) compared to the rule of mixture is observed, reaching a total strength of 1.69 GPa. We present a model that serves as a design guideline for such synergetically deforming nano-hybrid materials.

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On strain hardening mechanism in gradient nanostructures

Cited by 229 publications

References 60 publications

A Review on Heterogeneous Nanostructures: A Strategy for Superior Mechanical Properties in Metals

A Review on Heterogeneous Nanostructures: A Strategy for Superior Mechanical Properties in Metals

Eliminating deformation incompatibility in composites by gradient nanolayer architectures

Large strain synergetic material deformation enabled by hybrid nanolayer architectures

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