Mechanical Behavior of Nanostructured Materials: Poster Session
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Xinghang Zhang, Purdue University; Yuntian Zhu, North Carolina State University; Joseph Poon, University of Virginia; Suryanarayana Challapalli, University of Central Florida; Enrique Lavernia, University of California, Irvine; Haiyan Wang, Texas A&M University

Tuesday 6:00 PM
February 28, 2017
Room: Hall B1
Location: San Diego Convention Ctr

Funding support provided by: AJA International; Hysitron Inc.

Session Chair: Joseph Poon, University of Virginia; Yuntian Zhu, North Carolina State University; Deliang Zhang, Shanghai Jiaotong University; Zhe Fan, Texas A&M University

L-121: Cyclic Response of Friction-stir Processed Ultra-fine Grained Copper: Salar Salahi1; G. Guven Yapici1; 1Ozyegin University
    Friction processing has become a viable method of refinement down to ultra-fine and nanostructured regime, especially in the stir zone. It is also possible to obtain sound joints of similar and dis-similar materials with this technique. Reliable utilization of friction stir welded joints with ultra-fine grained microstructure requires attention on the fatigue behavior as well. In this work, cyclic response of pure copper at different joint zones was investigated. Fatigue properties were demonstrated with the S-N curves developed under positive mean stress. Fatigue properties were specified at a strain ratio of 0.1 with total strain amplitudes up to 0.2%. The results demonstrated cyclic hardening at high strain amplitudes, while softening was observed at low strain amplitude of 0.01%. The hysteresis loops indicated the concavity along with the small portion of linear behavior after the reversal point. Fatigue properties at various conditions were discussed in light of the respective failure mechanisms.

L-122: Projectile Induced Deformation Twinning in Nanocrystalline Aluminum: Sichuang Xue1; Zhe Fan1; Olawale Lawal2; Thevamaran Ramathasan2; Yue Liu3; Kaiyuan Yu4; Edwin Thomas2; Xinghang Zhang5; 1Texas A&M University; 2Rice University; 3Los Alamos National Laboratory; 4China University of Petroleum; 5Purdue University
    It has been shown both experimentally and computationally that deformation twinning and stacking faults form in nanocrystalline Al with high stacking fault energy. The response of nanocrystalline Al under shock loading remains less well understood. Here by using a micro-bullet enabled ballistic technique, we performed extensive microscopy studies on perforated nc Al films. Under the high-strain-rate deformation, deformation twins have been identified. Furthermore, broad incoherent twin boundaries were identified in perforated nanocrystalline Al. High-density dislocation networks have been observed in large grain (with a diameter exceeding 100 nm). Grain fragmentation and coarsening have also been identified.

L-123: Aluminum with High Modulus and Superior Strength by Self-Dispersed TiC Nanoparticles: Chezheng Cao1; Abdolreza Javadi1; Weiqing Liu2; Xiaochun Li1; 1University of California, Los Angeles; 2Harbin Institute of Technology
    Light metals (e.g. Al) matrix nanocomposites have tremendous potentials for automotive, aerospace, and military applications as they could offer low density, high specific strength, good stiffness and excellent thermal stability. It is also of fundamental interest to study mechanical behavior of such nanostructure material. However, the incorporation and dispersion nanoelement below 10 nm into metal matrix is a long-standing challenge. Here we report a way to synthesis TiC nanoparticles less than 10 nm in motel salt and then incorporated the nanoparticles into molten aluminum. A uniform distribution and dispersion of high loading TiC through a self-dispersion mechanism is achieved. Mechanical properties tests show the nanocomposites offer high Young’s modulus and superior strength. This scalable approach paves a way to mass produce high performance metal matrix nanocomposite with nanoelements (particles, plates and tubes) below 10 nm for a wide range of applications.

L-124: Multiscale Modeling of Deformation Behavior in Metal/Ceramic Mmultilayer Nanocomposites: Mohsen Damadam1; Iman Salehinia2; Georges Ayoub3; Hussein Zbib1; 1Washington State University; 2Northern Illinois University; 3University of Michigan-Dearborn
    Metal/ceramic multilayer (MCM) nanocomposites exhibit promising mechanical properties, i.e. high strength and high ductility, which vary with the individual layer thicknesses. Studying the mechanical behavior of MCM’s when the structure is composed of a great number of nano layers requires the implementation of some relations that can predict the material behavior correctly. Hence, molecular dynamics simulations results on MCM’s systems were used to develop a continuum model within the framework of viscoplasticity theory. The mechanical behavior of MCM nanocomposites is studied for different layer thicknesses depending on the controlling deformation mechanisms including Hall-Petch, confined layer slip, and dislocation nucleation mechanisms.

L-125: Competition between Slip and Martensitic Transformation of Retained Austenite in Carbon-steel/Copper Nanolaminates: Yadong Ru1; Yang Ren2; Lishan Cui1; Kaiyuan Yu1; 1China University Of Petroleum Beijing; 2X-ray Science Division, Argonne National Laboratory
    The ductility of steels with TRIP effects relies on the coupling between slip and transformation of retained austenite. Understanding the coupling mechanism is of great significance for the ductility enhancement of nanostructured steels. In this study, nanolamellar high-carbon-steel/copper composites are fabricated by hot pressing, rolling and wire drawing. Copper suppresses the growth of prior austenite (average size ~100nm) at elevated temperatures, and subsequent quenching and partitioning treatments result in a large amount of nanosized retained austenite phases, which in return enhance the plasticity of the materials to a maximum elongation of 60%. In situ tensile tests under synchrotron X-ray reveal that the transformation rate of retained austenite is much higher during the stress-induced regime than the strain-induced regime and the deformation mechanism of the composites is a result of the competition between transformation and slip of the retained austenite phases.

L-126: The Influence of Glassy Phase on the Crack Healing Efficiency of Silicon Carbide/Spinel Ceramic: Fariborz Tavangarian1; Guoqiang Li2; 1Penn State Harrisburg; 2Louisiana State University
    Crack self-healing behavior of SiC/MgAl2O4 nanocomposite was evaluated as a function of time, temperature and atmosphere. In the presence of oxygen at high temperatures, SiC reacts with oxygen to form SiO2 which is accompanied with about 80% volume expansion. On the other hand, the formed silica reacts with the matrix and produces some transition compounds which can rebond crack walls together. The results showed that complete healing can be obtained in the specimens sintered at 1550 °C for 1 min. Detailed investigation revealed that the formation of aluminosilicate glassy phase is responsible for the complete recovery of mechanical properties. At around 1550 °C, enstatite dissociated into forsterite and silica rich liquid which reacted with spinel and produced a glassy phase which can flow into the cracks and heal the structure. This glassy phase flows to the location of the cracks and acts as a glue. With decreasing the temperature this glassy phase provides a strong physical and chemical bonds between the crack walls and hence enhance the self-healing efficiency of the composite.

L-128: The Thermal Stability of Cryomilled 5083 Aluminum Containing Diamantane Nanoparticles: Walid Hanna1; Khinlay Maung2; Mohammed Enayati3; James Earthman4; Farghalli Mohamed4; 1Military Technical College; 2Precision Castparts Corp.; 3Department of Materials Engineering, Isfahan University of Technology, ; 4Department of Chemical Engineering and Materials Science, University of California, Irvine
    Cryomilling of Al alloys results in a grain sizes ranging from 20 to 50 nm. However, the nanoscale grain size cannot be retained upon annealing making consolidation of the powders impractical. A novel approach to enhance the thermal stability of cryomilled Al alloy powders is to disperse nanoscale molecular additions onto the grain boundaries and grains via the cryomilling process. The validity of this approach was examined by adding diamantane nanoscale diamond molecules to 5083 Al during cryomilling. The experimental results showed that the average grain size for all powders containing 0.5 % diamantane remained in the nanocrystalline range for all exposures temperatures ranging from 473K to 773K for various time intervals. The observed grain sizes were also consistently less than those for cryomilled 5083 Al without diamantane annealed under the same conditions. The thermal stability due to the presence of diamantane is qualitatively explained in terms of Zener’s concept.

L-129: Dynamic Behavior of Ultra High Molecular Weight Polyethylene Reinforced with Ceramics Nanoparticles at High Strain Rates: Édio Lima Júnior1; Sergio Monteiro1; Ricardo Weber1; Alaelson Vieira1; 1Military Institute of Engineering
    The dynamic behavior is an important characteristic when a material the specimen is subjected to high strain rates. Ultra high molecular weight polyethylene (UHMWPE) is a material that can be used for ballistic protection. In order to improve the UHMWPE response, a composite was fabricated with ceramic nanoparticles dispersed in UHMWPE matrix. In the present work, thermal, mechanical, XRD and SEM techniques were employed to evaluate the composite characterization. Additionally, dynamic behavior under high strain rates conditions were evaluated with split Hopkinson bar tests. The results were compared with uncharged UHMWPE similarly processed. The results showed that the composite has better response than the uncharged polymer and the mechanism responsible for improving performance.

L-130: Molecular Dynamics Study of the Creep Behavior of Metallic Glasses and Glass-composites: Constanze Kalcher1; Tobias Brink1; Jochen Rohrer1; Alexander Stukowski1; Karsten Albe1; 1Technische Universität Darmstadt
    In contrast to crystals, where one can clearly distinguish between three different creep stages, the mechanism behind the high-temperature creep behavior of amorphous alloys is still unclear. In this work we present Molecular Dynamics simulations on the creep behavior of Cu64Zr36 metallic glass which is a prototypical binary glass former that is well described by EAM potentials. We analyze how the creep rate is altered in the presence of secondary crystalline CuZr-B2 phases, which are known to enhance the mechanical properties at room temperature. As opposed to the pristine glass, creep resistance is decreased in the composites. Moreover, it can be observed that not only the size of the interface, but also the topology of the secondary phase plays a strong role in the creep behavior of the composites. We propose an explanation in terms of different mean Schmid factors of the interfaces.

L-131: Dislocation Engineering in Novel Nanowire Structures: Chris Chow1; Sam Reeve1; Alejandro Strachan1; 1Purdue University
    Leveraging defects is a cornerstone of materials science, and has become increasingly important from bulk to nanostructured materials. We use molecular dynamics simulations to explore the limits of defect engineering by harnessing individual dislocations in nanoscale metallic specimens and utilizing their intrinsic behavior for application in mechanical dampening. We study arrow-shaped, single crystal copper nanowires designed to trap and control the dynamics of dislocations under uniaxial loading. We characterize how nanowire cross-section and stacking-fault energy of the material affects the ability to trap partial or full dislocations. Cyclic loading simulations show that the periodic motion of the dislocations leads to mechanical dissipation even at frequencies up to 2x10^10 Hz, orders of magnitude higher than the current state of the art.

L-132: An Experimental Investigation of Deformation Mechanisms in FCC Thin Films: Marissa Linne1; Samantha Daly2; 1University of Michigan; 2University of California, Santa Barbara
    This presentation will discuss an on-going investigation into the mechanical behavior of, and the interactions between slip and grain boundary sliding, in oligocrystalline Al thin films under uniaxial tensile loading. The hypothesis under examination is that slip at/near grain boundaries and grain boundary sliding are coupled, synergistic processes. Due to their nanoscale thickness and columnar grain structure, oligocrystalline Al films can be approximated as two-dimensional specimens, enabling characterization of dislocation glide and GBS mechanisms without sub-surface ambiguity. In this investigation, Al films with thicknesses of hundreds of nanometers were tested in-SEM under uniaxial tension through use of a custom MEMS actuator, and full-field surface displacements were measured using a high-resolution combination of scanning electron microscopy and distortion-corrected digital image correlation. Analysis of the resulting full-field data linking deformation behavior and underlying texture is used to inform crystal plasticity models provided insight into the interaction between GBS and dislocation-based deformation mechanisms.

L-133: Impact of Heat Treatments at Varying Temperature on the Strength and Ductility of Nanotwinned Inconel: Nathan Heckman1; Andrea Hodge1; 1University of Southern California
    There has been much interest recently in nanotwinned metals due to their potential for simultaneous high strength and ductility. In this study, fully nanotwinned columnar Inconel has been synthesized by magnetron sputtering with an average twin thickness on the order of nanometers and grain width on the order of hundreds of nanometers. While the as sputtered film shows tensile strengths up to 2.5 GPa, there is very limited ductility. Heat treatments up to 800° C were performed on the sputtered films in order to tune the mechanical behavior. Microstructural characterization of the heat treated films were performed at each temperature and tensile tests were performed on each film in order to determine the impact heat treatment temperature has on strength and ductility and to understand how the observed microstructures contribute to the mechanical behavior.

L-134: Mechanical Characterization of fcc and bcc Metals by Extraction of Nanoindentation Stress-strain Curves: Alexander Leitner1; Verena Maier-Kiener1; Reinhard Fritz1; Daniel Kiener1; 1Montanuniversität Leoben
    The extraction of stress-strain curves from nanoindentation measurements has been widely investigated and would be a beneficial tool, especially when material is limited. Various approaches, such as the use of different shaped indenter tips as well as finite element simulations have shown promising results. However, a direct comparison of those methods on a broad range of materials and microstructures has not yet been examined. This study will provide new insights into the feasibility of these techniques by investigating a comprehensive set of materials including face-centered cubic and body-centered cubic metals with microstructures spanning from a single crystalline to a nanocrystalline length scale. We will demonstrate that once the ratio of yield strength to modulus and exact tip shape are considered in the analysis, nanoindentation is a unique and convenient tool to extract true stress-strain curves of metals at a small-scale, and that the mentioned approaches deliver comparable results.

L-135: Multi-stages Spiral Twist Extrusion: A Novel Severe Plastic Deformation Technique for Bulk Nanostructured Materials: Waleed El-Garaihy1; Dina Fouad2; Hanadi Salem2; 1Qassim University; 2American University in Cairo
    In this study, an innovative technique of severe plastic deformation named Multi-stages Spiral Twist Extrusion (MSTE) was designed to produce bulk nanostructured materials (BNM). The principle of MSTE was adopted to guarantee shear strain accumulation within a square cross-section workpiece without undergoing dimensional or shape change. The induced total effective strain via MSTE is a function of the length of the twist extrusion zone, the die slop angle, the angle of the outlet zone relative to the twist angle and the number of passes. Accordingly, MSTE is capable of producing ultrafine nanoscale structure with variable texture. In an attempt to evaluate the cumulative strain associated with MSTE for different alloy rods with variable cross-sectional areas are processed at different deformation temperatures and strain rates. Evaluation and validation of the novel process is conducted via series of investigation of the mechanical behavior and structural evolution before and after processing.

L-136: Superelasticity, Micaceous Plasticity and Size Effects of Novel Intermetallic Compound CaFe2As2 At Small Length Scales: John Sypek1; Christopher Weinberger2; Paul Canfield3; Sergey Bud'ko3; Seok-Woo Lee1; 1University of Connecticut; 2Drexel University; 3Iowa State University
    Shape memory materials (SMMs) have the capability to recover their original shape after plastic deformation when they are subjected to certain stimulus. Here, we report the first discovery of SMM behavior in a novel intermetallic compound CaFe2As2. We fabricated micropillars out of single crystals of CaFe2As2, and conducted in-situ micropillar compression test. CaFe2As2 exhibits unprecedented superelasticity: over 13% recoverable strain without any residual fatigue damage, yield strengths over 3.5 GPa at room temperature, and has potential to show cryogenic linear shape memory effects at low temperatures by the reversible phase transformation between tetragonal/orthorhombic to collapsed tetragonal phase. Also, this material exhibits strong anisotropy in plasticity. Superelasticity and micaceous plasticity as a function of micropillar diameter was investigated. This represents a new class of smart materials with a set of properties that includes the highest actuation work per volume reported and has potential for space applications.

L-138: Manipulating the Grain Boundary Structure of an Ultrafine Grained Cu-Zr Alloy to Enhance Strain Hardening Capability and Strength: Dengshan Zhou1; Deliang Zhang1; 1Northeastern University
    The nanocrystalline and ultrafine grained metallic materials normally lack strain hardening ability due to rapid dynamic recovery of dislocations at boundaries of nanometer and submicron grains. Due to this effect, these materials just show a uniform strain of 2-3% before reaching their ultimate tensile strength during tensile tests. We found that the strain hardening capability of an ultrafine grained Cu-Zr alloy, produced by a combination of spark plasma sintering and hot rolling, can be substantially improved via the formation of a unique grain boundary structure. The plastic strain of the uniform deformation stage (6-8%) of the sample with the unique grain boundary structure during tensile testing was two times that of the as-rolled sample, making the former achieve a clearly higher tensile strength.

L-139: Enhanced Mechanical and Electrical Properties of Nanocrystalline Cu Matrix Nanocomposite with In-situ Formed NbC Nanoparticles: Wei Zeng1; Dengshan Zhou1; Deliang Zhang1; 1Shanghai Jiaotong University
    Nanocrystalline Cu-6.4vol.%NbC nanocomposite with grain size of about 96 nm containing in-situ formed NbC particles of about 6.1 nm was successfully fabricated through high energy mechanical milling, cold pressing, vacuum sintering and hot extrusion. The mechanical and electrical properties of the nanocomposite are outstanding, reflected by a tensile strength of 868 MPa, an elongation to failure of 5.3%, and an electrical conductivity of about 56% international annealed copper standard (IACS). The material exhibited ultrahigh thermal stability, with limited grain growth from 96 to 165 nm after annealing the sample at 1000 ˚C for 50 h, though the average size of the NbC nanoparticles increased dramatically from 6 to 29 nm. The high strength of the nanocomposite is ascribed to the concurrent effects of both grain boundary strengthening and nanoparticles strengthening, the good tensile ductility maybe due to the resistance to deformation instability through the interactions between NbC nanoparticles and dislocations.

L-140: Effects of the Angle between Micro-crack and Loading Direction on Crack Propagation of Single Crystal γ-TiAl Alloy: Ruicheng Feng1; Jiantao Lu1; Haiyan Li1; Hui Cao1; Zhiyuan Rui1; 1Lanzhou University of Technology
     Molecular dynamics simulation is employed to make the model of crack propagation for single crystal γ-TiAl alloy. The effects of the angle between micro-crack and loading direction on crack propagation are studied. When the angle is 0°, the first dislocation is emitted at t=86ps. As for 45° and 90°, the first dislocation is emitted at t=66ps and at t=63ps respectively. When the dislocations slip, there are intrinsic stacking faults, Hirth locks and Lomer-Cottrell locks formed and with the increasing angle, the number of them decreases. Stacking fault tetrahedral appears only in the model with 0°. As the crack extends, fracture firstly occurs when the angle is 90° and as for 0°, fracture finally occurs. Comparing the stress–strain curves for three angles of 0°, 45° and 90° shows that as the angle increases, the critical stress decreases from 9.36GPa to 7.91GPa. The corresponding strain also reduces from 9.4% to 6.93%.

L-141: Tensile Properties of Perovskite in Flexible Solar Cells: Seung-min Ahn1; Eui Dae Jung1; Myoung Hoon Song1; Ju-Young Kim1; 1UNIST
    Photovoltaic energy is currently drawing attention as an upcoming alternative energy source, and perovskite solar cells hold promise for next-generation photovoltaic devices due to their remarkable optical properties, high light-absorption coefficient and good cost-effectiveness. However, these materials are still afflicted with long-term stability and reliability issues. To commercialize this device, understanding of its mechanical behavior is of high priority. Many researchers have attempted to solve its stability issues, but information on its mechanical properties is still insufficient. For this reason, we fabricate free-standing component thin films of perovskite solar cells and evaluated their elastic properties using in-situ nanoindentation tests on hole-substrates. We confirmed that the perovskite layer is most fragile layer among all components. Therefore, we evaluated and analyzed the intrinsic tensile properties of perovskite layer by in-situ tensile testing using push-to-pull devices. We believe that this study sheds light on the durability and fundamental mechanisms of the material.

L-142: Fabrication and Characterization of Aluminum-carbon Nanotubes (Al-CNT) Functionally Graded Cylindrical Composites: Amal Esawi1; Ehab Salama1; Sherry Morad2; 1American University in Cairo; 2American University in Cairo
    The current investigation focuses on functionally-graded (FG) Aluminum-Carbon Nanotube composites (Al-CNT) with the goal of obtaining a desirable trade-off between the material strength and its ductility at the lowest possible reinforcement concentrations to reduce overall cost. In this study we developed a new simple manufacturing route to fabricate coaxial multilayered FG composite structures using powder metallurgy methods. Different FG layer configurations were investigated. Preliminary mechanical tests showed around 50% increase in the material’s strain at failure and 30% increase in the compressive strength for FG structures with 1% wt. and 2% wt. of overall CNT contents, respectively, as compared to Al-CNT composites with uniformly dispersed CNTs having the same reinforcement concentrations. The novel structure and geometry of the produced FG cylindrical composites could be of interest to applications which require high surface strength combined with high overall ductility while keeping the cost of the composite as low as possible.

L-143: High Strength and High Conductivity Wires Made from Cu-Ag Alloys Designed for the Construction of High Magnetic Fields Generators: Eliza Sieja-Smaga1; Artur Kawecki1; Tadeusz Knych1; Andrzej Mamala1; Krystian Franczak1; Kinga Korzeń1; Grzegorz Kiesiewicz1; Paweł Kwaśniewski1; 1AGH University of Science and Technology
    This paper presents the results of experimental research on the evolution of the set of high strength and electrical properties of Cu-Ag (3-15 wt.%) alloys. Continuous melting and casting process of rods and the drawing process of wires using pre- and inter-operation of multi-stage heat treatment in order to improve the mechanical (UTS=900-1600 MPa) and electrical (63-90 % in IACS scale) properties of circular and profiled cross-section wires has been presented. Metallographic analysis for casts, drawn wires and wires after heat treatment was performed with the use of SEM and TEM microscopy presented in the paper. Effect of different kind of microstructure and the value of deformation on electrical conductivity of the wires during low temperature tests were presented. Model calculations and a construction of the electromagnet coils made of wires with Cu-Ag alloys and the results of the tests carried out at cryogenic temperature has been also shown.

L-144: Mechanical Characterization of Cold Sprayed Aluminum Alloy Using Micropillar Compression: Tyler Flanagan1; Benjamin Bedard1; Sumit Suresh1; Mark Aindow1; Avinash Dongare1; Harold Brody1; Xuemei Wang2; Victor Champagne3; Seok-Woo Lee1; 1University of Connecticut; 2United Technologies Research Center; 3U.S. Army Research Laboratory
    The mechanical characterization of shocked materials is of great interest since the severe deformation process creates unusual microstructure, resulting in unique mechanical properties. Here, we will present the mechanical properties of single-pass cold spray trials of Al-6061 microparticles onto substrates of the same alloy with a velocity of ~1 km/s. The mechanical properties of these splats have been studied by utilizing in-situ micro-pillar compression in scanning electron microscope. We found a strong size effect in the submicron diameter range, but negligible size effect in pillars above 1 um in diameter. We explain these two distinct size effect regimes in terms of microstructural length scales such as grain/dendrite size, precipitation, and dislocation densities. We compared these findings with the micro-mechanical properties of undeformed single Al alloy particles. This study will give an insight in fundamental understanding in high strain rate deformation mechanisms in aluminum alloys.