References of "Acta Materialia"
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See detailQuasicontinuum study of the shear behavior of defective tilt grain boundaries in Cu
Péron-Lührs, Vincent ULg; Sansoz, Frédéric; Noels, Ludovic ULg

in Acta Materialia (2014), 64

Atomistic simulations using the quasicontinuum method are used to study the role of vacancy defects and angström-scale voids on the mechanical behavior of five tilt bicrystals containing grain boundaries ... [more ▼]

Atomistic simulations using the quasicontinuum method are used to study the role of vacancy defects and angström-scale voids on the mechanical behavior of five tilt bicrystals containing grain boundaries (GBs) that have been predicted to exhibit characteristic deformation processes of nanocrystalline and nanotwinned metals: GB-mediated dislocation emission, interface sliding, and shear-coupled GB migration. We demonstrate that such nanoscale defects have a profound impact on interfacial shear strength and underlying deformation mechanisms in copper GBs due to void-induced local stresses. In asymmetric high and low angle GBs, we find that voids become preferential sites for dislocation nucleation when the void size exceeds 4 Å. In symmetric 9(221) GBs prone to sliding, voids are shown to shield the local shear stress, which considerably reduces the extent of atom shuffling at the interface. In symmetric Sigma5(210) and Sigma27(115) GBs, we find that the effect of voids on shear-coupled GB migration depends on the GB tilt direction considered, as well as on the size and number of voids. Remarkably, large voids can completely abate the GB migration process in Sigma 27(115) GBs. For all GB types, the interfacial shear strength is shown to decrease linearly as the volume fraction of voids at the interface increases; however, this study also suggests that this decrease is much more pronounced in GBs deforming by sliding than by dislocation nucleation or migration, owing to larger void-induced stresses. [less ▲]

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See detailMultifunctional hybrids for electromagnetic absorption
Huynen, Isabelle; Quievy, N.; Bailly, Christian et al

in Acta Materialia (2011), 59(8), 3255-3266

Electromagnetic (EM) interferences are ubiquitous in modern technologies and impact on the reliability of electronic devices and on living cells. Shielding by EM absorption, which is preferable over ... [more ▼]

Electromagnetic (EM) interferences are ubiquitous in modern technologies and impact on the reliability of electronic devices and on living cells. Shielding by EM absorption, which is preferable over reflection in certain instances, requires combining a low dielectric constant with high electrical conductivity, which are antagonist properties in the world of materials. A novel class of hybrid materials for EM absorption in the gigahertz range has been developed based on a hierarchical architecture involving a metallic honeycomb filled with a carbon nanotube-reinforced polymer foam. The waveguide characteristics of the honeycomb combined with the performance of the foam lead to unexpectedly large EM power absorption over a wide frequency range, superior to any known material. The peak absorption frequency can be tuned by varying the shape of the honeycomb unit cell. A closed form model of the EM reflection and absorption provides a tool for the optimization of the hybrid. This designed material sets the stage for a new class of sandwich panels combining high EM absorption with mass efficiency, stiffness and thermal management. [less ▲]

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See detail2-Point correlation function of nanostructured materials via the grey-tone correlation function of electron tomograms: A three-dimensional structural analysis of ordered mesoporous silica
Gommes, Cédric ULg; Friedrich, Heiner; De Jongh, Petra E et al

in Acta Materialia (2010), 58

Electron tomography is a unique technique for imaging the microstructure of materials with a nanometer resolution. The signal to noise ratio of electron tomograms is, however, often too low for a reliable ... [more ▼]

Electron tomography is a unique technique for imaging the microstructure of materials with a nanometer resolution. The signal to noise ratio of electron tomograms is, however, often too low for a reliable segmentation-based image analysis. We derive a general relation between the grey-tone correlation function of the tomograms and the 2-point correlation function of the morphology, which enables to analyze quantitatively the grey-tone correlation function with a morphological model of the material. The methodology is applied to SBA-15 ordered mesoporous silica. The three-dimensional grey-tone correlation function obtained from electron tomography is analyzed in terms of a hexagonal array of Gaussian independent pores. The model enables to relate the morphology obtained from the 2-point correlation function to macroscopic characterization data of the material, notably small-angle X-ray scattering and nitrogen adsorption. [less ▲]

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See detailModelling compression tests on aluminium produced by equal channel angular extrusion
Poortmans, Stijn; Duchene, Laurent ULg; Habraken, Anne ULg et al

in Acta Materialia (2009)

The main objective of this paper was to characterize the mechanical properties of commercial purity aluminium AA1050 after being submitted to the equal channel angular extrusion (ECAE) process ... [more ▼]

The main objective of this paper was to characterize the mechanical properties of commercial purity aluminium AA1050 after being submitted to the equal channel angular extrusion (ECAE) process. Compression tests on cylindrical samples extracted from ECAE material are extensively described. The influence of ECAE conditions (number of passes, route, etc.) on the mechanical response is assessed. The extraction of the material behaviour from the experimental results is not straightforward because of inhomogeneities occurring during the test. Therefore, an inverse modelling with the finite element method was used to obtain accurate material parameters by optimization. It appeared that an accurate material yield locus (based on texture analysis) is necessary in order to reproduce the anisotropic behaviour of the ECAE material. On the other hand, its hardening behaviour during compression tests was satisfactorily represented by an elastic (near) perfectly plastic model. [less ▲]

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See detailInterests and limitations of nanoindentation for bulk multiphase material identification: Application to the β phase of Ti-5553
Gerday, Anne-Françoise ULg; Ben Bettaieb, Mohamed ULg; Duchene, Laurent ULg et al

in Acta Materialia (2009), (57), 5186-5195

This paper focuses on the numerical modeling of nanoindentation tests. The first goal of this study is to collect essential material parameters and boundary conditions from the literature and to complete ... [more ▼]

This paper focuses on the numerical modeling of nanoindentation tests. The first goal of this study is to collect essential material parameters and boundary conditions from the literature and to complete the data required to accurately model nanoindentation tests. The second goal of this study consists in validating the material parameters identified from macroscopic tensile tests of the body-centered cubic b phase of Ti-5553, a new generation of titanium alloy. This validation is performed looking at experimental and numerical nanoindentation curves obtained for different grain orientations. [less ▲]

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