Multiscale Architectured Materials (MAM II): Tailoring Mechanical Incompatibility for Superior Properties: Novel and Complex Materials II
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Yuntian Zhu, North Carolina State University; Irene Beyerlein, University of California, Santa Barbara; Yves Brechet, Grenoble Institute of Technology; Huajian Gao, Brown University; Ke Lu, Institute of Metal Research, Chinese Academy of Science; Xiaolei Wu, Institute of Mechanics, Chinese Academy of Science

Thursday 8:30 AM
March 2, 2017
Room: 24B
Location: San Diego Convention Ctr

Session Chair: Hyoung Seop Kim, POSTECH; X. Wendy Gu, UC Berkeley

8:30 AM  Invited
Properties of Metallic Lattices Used as Hosting Structures: Guilhem Martin1; Oleg Liashenko1; Damien Fabrègue2; Didier Bouvard1; Rémy Dendievel1; Jean-Jacques Blandin1; 1Univ. Grenoble Alpes; 2Univ. Lyon
    Elaboration of metallic lattice structures has received increasing attention in the recent past. Besides the choice of constitutive material and relative density, the choice of the lattice architecture affects the mechanical properties of the structures. An important issue for predicting properties is also to get information about the geometry of the produced structure, which can differ to what was expected and depend on the processing route. An example will be detailed in the case of a TA6V structure produced by additive manufacturing. The mechanical efficiency of such a lattice will be discussed in relation with building and melting strategies. Such lattice structures can be used as it but they can also be used as hosting structures. For example, they can be filled by a metallic powder, to be completely or partially sintered, leading to hybrid materials allowing to reach properties difficult to reach in the case of conventional materials.

8:55 AM  
Multiscale Architectured Materials with Composition and Grain Size Gradients Manufactured Using High-pressure Torsion: Hyoung Seop Kim1; 1POSTECH
    The concept of multiscale architectured materials is established using composition and grain size gradients. Composition-gradient nanostructured materials are produced from coarse grained interstitial free steels via carburization and high-pressure torsion. Quantitative analyses of the dislocation density using X-ray diffraction and microstructural studies clearly demonstrate the gradients of the dislocation density and grain size. The mechanical properties of the gradient materials are compared with homogeneous nanostructured carbon steel without a composition gradient in an effort to investigate the gradient effect. Based on the above observations, the potential of multiscale architecturing to open a new material property is discussed.

9:15 AM  Cancelled
A Design Concept for Tough, Strong and Damage-tolerant Composites by Utilizing the Yield Stress Inhomogeneity Effect: Masoud Sistaninia1; Otmar Kolednik2; 1Materials Center Leoben Forschung GmbH; 2Erich Schmid Institute of Materials Science, Austrian Academy of Sciences
     Recent investigations have shown that the yield stress inhomogeneity effect can be applied as an innovative method for designing new, tough and flaw-tolerant materials [1, 2]. The mechanism is the strong decrease of the crack driving force when the crack tip is located in the soft region, near the boundary to the hard matrix material. This can lead to crack arrest, if the material properties, the spacing, and the thickness of the soft interlayer region are appropriately chosen. For example, a combination of numerical studies with the configurational forces concept with fracture mechanical derivations shows that the optimum interlayer spacing is load dependent. A procedure is introduced, how the optimum architectural parameters can be found. References: [1] M. Sistaninia, O. Kolednik, Eng. Fract. Mech. 130, 2014.[2] O. Kolednik, J. Zechner, J. Predan, Scripta Materialia 113, 2016.

9:35 AM  
Self-assembled Nanoparticle Superlattices with High Elastic Modulus: X. Wendy Gu1; David Koshy1; Xingchen Ye1; Paul Alivisatos1; 1UC Berkeley
    Architectured materials made from nanoscale building blocks often exhibit extraordinary mechanical properties, but are difficult to fabricate with conventional techniques. Here, colloidal self-assembly is used to arrange polystyrene-grafted Au nanoparticles at a fluid interface to form ordered nanoparticle solids, or superlattices, with sub-10 nm features but overall dimensions of ~1 cm. A thin film buckling method is used to measure superlattice elastic modulus, which was as high as 120 GPa for a superlattice with 12 vol. % Au. Superlattices consisting of a single monolayer of nanoparticles have higher elastic moduli than superlattices with multilayer thicknesses. Additionally, elastic modulus is enhanced for superlattices that are self-assembled rapidly, which leads to structural defects like nanoparticle vacancies, dislocations and grain boundaries. We propose that the exceptional stiffness of self-assembled nanoparticle superlattices stems from the extreme confinement of polystyrene molecules between Au nanoparticles that arises during the highly non-equilibrium self-assembly process.

9:55 AM  
Multi-scale Modelling of Mechanical Behavior and Deformation in Materials with Gradient Microstructures: Hao Lyu1; Mehdi Hamid1; Annie Ruimi2; Hussein Zbib1; 1Washington State University; 2Texas A&M at Qatar
    Materials with gradient microstructures have attracted considerable attention due to their improved ductility and strength. In this work, we focus on modeling the deformation mechanisms of gradient material using a dislocation-based multi-scale model coupled with a stress/strain gradient theory. The multi-scale framework is consists of a viscoplastic self-consistent model coupled by continuum dislocation dynamic. Nano-gradient materials with a "bamboo structure" are studied. The mechanical responses of these gradient structures are compared with their equivalent homogeneous microstructure cases and experiments. The simulation results show that gradient materials can achieve high strength and ductility simultaneously, and are in good agreement with experimental results found in the literature.

10:15 AM Break

10:30 AM  Invited
Multi-scale Cu/Nb Nanocomposite Wires Processed by Severe Plastic Deformation for High Pulsed Magnets: Assessing Size and Architecture Effects on the Resistance to High Stress: Ludovic Thilly1; Florence Lecouturier2; Jean Rony Medy1; Patrick Villechaise1; Pierre-Olivier Renault1; 1Pprime Institute - University of Poitiers; 2LNCMI
     Cu/Nb high-strength and high-electrical conductivity nanocomposite wires are prepared by severe plastic deformation, applied with an Accumulative Drawing and Bundling process (ADB), for the windings of high pulsed magnets. The ADB process leads to a multi-scale Cu matrix containing up to N=854 (52.2 106) continuous parallel Nb filaments with diameter down to few tens nanometers. After heavy strain, the Nb filaments exhibit a homogeneous microstructure with grain size below 100 nm. The Cu matrix presents a multi-scale microstructure with multi-modal grain size distribution from the micrometer to the nanometer range. The use of complementary characterization techniques at microscopic and macroscopic scales (EBSD, in-situ TEM tensile tests, in-situ tensile tests under neutrons or synchrotron beam) shed light on the individual roles of the microstructure and its multi-scale nature in the recorded extreme mechanical properties.[Acta Mat, 57 (2009), p3157; Acta Mat, 58 (2010), p6504; Adv. Eng. Mat., 14-11 (2012), p998].

10:55 AM  Invited
The Thermal-mechanical Compromise for Insulation Materials: Bernard Yrieix1; 1EDF R&D
    The thermal insulation materials are very porous ( > 90 or 95 % in most of the case). In addition the super-insulation materials (conductivity < 25 mW/(m.K)) are nanostructured in order to benefit from the Knudsen mode of gaseous conduction. Their main property is of course the thermal behaviour but such materials have to satisfy to minimal mechanical properties so as to be manufactured, carried, installed and finally used. Owing to the thermal / mechanical antagonism this asymmetric multifunctionality is not obvious to deal with. Improving the compromise remains a challenge and a practical goal because of the impact on the cost of the performance. To illustrate this challenge and some ways of improvement through the material architecturation, my talk will give some examples in the fields of traditional and super insulation materials.

11:20 AM  
Impact Behavior of Lattice Structures Produced by Selective Laser and Electron Beam Melting: Pauline Delroisse1; Nicolas Bruzy2; Olivier Rigo3; Sébastien Michotte3; Eric Maire4; Jérôme Adrien4; Pascal Jacques1; Thierry Massart5; Aude Simar1; 1Université Catholique de Louvain; 2Ecole Centrale de Nantes; 3Sirris; 4Institut National des Sciences Appliquées de Lyon; 5Université Libre de Bruxelles
    The fast development of additive manufacturing technologies allows the optimization of lattice structures in particular, in the present study, for impact energy absorption. Since their properties depend on parameters such as build material or core morphology, the project compares different combinations: strut geometry (various diameter and roughness reduced through chemical etching), materials (AlSi10Mg or Ti-6Al-4V), processed by two metal additive manufacturing techniques (SLM or EBM), covered or not by Al2024 plates and with or without post-treatment. The deformation mechanisms after compression and impact tests are characterized in particular by 3D X-ray tomography. The structures may thus be optimized in order to delay failure. In addition, a simplified model based on beam theory allows understanding the static and dynamic behaviors of these lattice structures.