Compatible deformation and extra strengthening by heterogeneous nanolayer composites (original) (raw)
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scripta materialia, 2020
A topologically heterogeneous microstructure design is introduced in a Cu/Zr nanolayered composite, in which each soft 100 nm Cu or Zr layer is surrounded on both sides by several hard 10 nm Cu/Zr bilayers. This design aims to impose a full geometrical constraint on all of the soft layers. Micropillar compression tests demonstrate that the composite deforms in a compatible fashion among the layers, in which no extrusion of the soft layers occurs. An elevated strength of 730 MPa is achieved in the composite compared with the strength prediction based on the linear rule of mixtures.
Eliminating deformation incompatibility in composites by gradient nanolayer architectures OPEN
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.
Large strain synergetic material deformation enabled by hybrid nanolayer architectures
Scientific Reports
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.
Large strain synergetic material deformation enabled by hybrid nanolayer architectures OPEN
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.
Structure and mechanical behavior relationship in nano-scaled multilayered materials
MRS Proceedings, 2001
ABSTRACTMultilayered foils with 10%Cu/90%Ni and different bi-layer thickness (100-1000 nm) have been fabricated by electrodeposition. TEM and x-ray diffraction analysis indicate discrete layer formation and a (100) textured structure. The maximum tensile strength (590 MPa) is obtained for foils with the smallest layer thickness. Preliminary results on high temperature deformation show a strong dependence of strength and plasticity on layer thickness.
Applied Physics Letters, 2009
We investigate the deformation behavior of bimetallic and trimetallic nanoscale multilayer metallic composites under biaxial loading using molecular dynamics. Three types of structures were studied: ͑a͒ Cu-Ni fcc/fcc bilayer, ͑b͒ Cu-Nb fcc/bcc bilayer, and ͑c͒ Ni-Cu-Nb fcc/fcc/bcc trilayer. A configuration with a dislocation structure inside is generated by initially loading a perfect structure to a high strain to nucleate dislocations, then completely unloading it and loading it again. The comparison between the deformation behavior of bilayer and trilayer structures revealed that the Cu-Ni is more ductile, the Cu-Nb is stronger, and the trilayer structure exhibits both high strength and ductility.
2014
Comparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoid thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak bro...
Size effects on the Mechanical Behavior of Nanometric W/Cu Multilayers
MRS Proceedings, 2008
Le comportement mécanique de multicouches W/Cu nano structurées préparées par pulvérisation ionique a été analysé en utilisant une méthode combinant la diffraction des rayons X et la déformation in situ. Les essais on été réalisés sur une source de lumière synchrotron pour analyser la réponse élastique du tungstène. Trois différentes microstructures on été analysées : l'échantillon composé de la couche de tungstène la plus fine présente un comportement mécanique différent de celui attendu pour un matériau massif. Néanmoins, des mesures par microscopie électronique en transmission (MET) et par diffusion centrale en incidence rasante (GISAXS en anglais) révèlent des discontinuités dans les sous-couches de cuivre. Comme les déformations de ces clusters de cuivre et les contributions des joints de grain ne sont pas expérimentalement accessibles, une approche par simulation atomistique devient indispensable.
Journal of Applied Physics, 2012
The strain hardening and the related surface pile-up phenomena in CuNi, CuNb and CuNiNb nanoscale multilayered metallic (NMM) composites are investigated using atomistic simulations of nanoindentation on such multilayers with varying individual layer thickness. Using empirical load-stress and displacement-strain relations, the obtained load-depth curves were converted to hardness-strain curves which was then fitted using power law. It is found that the extent of surface pile-up is inversely related to the hardening exponent of the NMMs. Two deformations mechanisms which control the surface pile phenomenon are discovered and discussed. Furthermore, from the stress-strain data, it is found that interfaces and their types play a major role in strain hardening; the strain hardening rate increases with strain when incoherent interfaces are present. The relationship between the hardening parameters and the interfacial dislocation density as well as the relationship between interfacial density and length scales, such as layer thickness and indentation depth, are analyzed, and it is found that the hardness in these NMM has strong inverse power law dependence on the layer thickness. V C 2012 American Institute of Physics. [http://dx.