Multiscale Architectured Materials (MAM II): Tailoring Mechanical Incompatibility for Superior Properties: Laminated Materials
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

Tuesday 2:00 PM
February 28, 2017
Room: 24B
Location: San Diego Convention Ctr

Session Chair: Mathias Göken, Universität Erlangen-Nürnberg; Christopher Schuh, MIT

2:00 PM  Invited
Multilayered and Functionally Graded Materials for Optimized Galvanic Corrosion Protection: Christopher Schuh1; Samuel Cross1; 1MIT
    In a galvanic corrosion setting, a graded material can expose a variety of corrosion potentials to an electrolyte whereas a monolithic material presents only one. The corrosion performance of such graded materials is complex and collaborative, and the concept opens a broad and highly nonlinear design space for new galvanic coatings with large potential performance benefits. This talk will present a new computational modeling and optimization paradigm for the design of next generation galvanic coatings. The combination of a variety of computational tools will be described; this includes conventional electrochemical continuum modeling, as well as new approaches to localized corrosion modeling via effective medium theory, and the introduction of optimization algorithms for rigorous coating design. The predictions of these methods will be shown to reproduce critical experimental results, and also to guide the development of new coating architectures with improved corrosion performance.

2:25 PM  Invited
High Temperature Plasticity of Cu-Cr Nanolayered and Chemically Nanostructured Cu-Cr Films: Gerhard Dehm1; T. Harzer1; C. Liebscher1; R. Raghavan1; 1Max-Planck-Institut für Eisenforschung
    This talk reviews the influence of microstructure evolution on the plasticity of Cu-Cr films using two microstructure concepts: nanolayering versus nanostructuring. PVD was used to create Cu-Cr nanolayered and alloyed films of identical composition. Alloyed films with 66at%Cu (Cu66Cr34) and Cu20Cr80 were found to form supersaturated solid solutions which consist only of bcc nanocrystals rather than fcc and bcc grains as thermodynamically expected. Advanced TEM studies reveal a hierarchical nanostructure for the bcc Cu66Cr34 alloy film: the supersaturated grains start to phase separate by spinodal decomposition leading to chemical gradients on the length-scale of a few nanometers. While the nanolayered Cu-Cr films reveal higher strength in microcompression testing at 25°C than the alloyed Cu-Cr films, they are more prone to diffusion assisted deformation at elevated temperatures. In contrast, the nanocrystalline grain size and chemical modulations within the supersaturated bcc grains lead to an improved mechanical performance at elevated temperature.

2:45 PM  Invited
Designing High Fracture Toughness Nanocomposites via In Situ TEM Approach: Nan Li1; Satyesh Yadav1; Xiang-Yang Liu1; Jian Wang2; Amit Misra3; Nathan Mara1; 1Los Alamos National Laboratory; 2University of Nebraska-Lincoln; 3University of Michigan, Ann Arbor
    Nucleation, motion and reaction of dislocations in crystalline materials are the elementary unit processes for understanding mechanical properties. Through in situ indentation of TiN in a high-resolution transmission electron microscope, dislocation nucleation behavior on {111} and {001} slip planes, the associated critical resolved shear stress for both nucleation and gliding have been explored. Different from the conventional reported ½<110>{110} slip system in TiN at room temperature, the nucleation of partial dislocation ⅙<112> on {111} has been captured. In order to favor the activation of multiple slip systems in TiN at room temperature, Al-TiN multilayered nanocomposites with designed interface orientation have been synthesized. Micro-mechanical testing indicated that when the individual layer thickness decreases to less than 5nm, the materials present enhanced fracture toughness due to plastic co-deformability of TiN layer with adjacent Al.

3:10 PM  
Laminar Bulk Metallic Glass/Metal Composites Via Accumulative Roll Bonding: Sina Shahrezaei1; Irene Beyerlein2; Stephanie O'Keeffe3; Suveen Mathaudhu1; 1University of California, Riverside; 2University of California, Santa Barbara; 3Liquidmetal Technologies
    Monolithic bulk metallic glasses (BMG) are known to have high strengths and hardness, however, they are inherently brittle, making them not desirable for structural applications wherein plastic deformation must be supported. Laminar composites of BMG and other ductile metals fabricated by deposition methods allow extraordinary mechanical performances including high ductility and strength, and unique dislocation activity in the amorphous/crystalline interface, however are limited in size and scalability. Here we demonstrate the scalable fabrication of laminar Zr-based BMG/Ni composites using accumulating roll bonding. The Mechanical behavior of these composites is evaluated using micro- and nanoindentation probes and mechanical tension tests. The resulting microstructures are evaluated using SEM and EBSD, while the composition at the bonding interface is analyzed using EDX. The effect of these novel interfaces on dislocation activity will be reported. The results forecast the design of a variety of BMG/crystalline metal composites for high performance structural materials.

3:30 PM Break

3:50 PM  
Effect of Initial Oxide Layer on the Growth and Morphology of Intermetallic Layer in Fe-based MIL Composites: Yu Wang1; Kenneth Vecchio2; 1North University of China; 2University of California San Diego
    Metal-intermetallic laminate composites can be designed for structural use to optimize the unique properties and benefits of the components, resulting in materials, which have the high strength and stiffness of the intermetallic with the high toughness of the metal. For fabricating the MIL composites, two kinds of metal foils are hot pressed with alternating layers in the open air and react around their lowest eutectic temperature until one of the foils has been consumed to form intermetallic phases. Initial oxide layer present at the surface of the metal foil strongly influences the nucleation and inter-diffusion process during the growth of the intermetallic, which will affect the microstructure and final properties of the MIL composites. This paper will focus on lower cost Fe-based MIL composites by examining the oxide layer effects on the initial nucleation stage, growth kinetics and the final morphology of the intermetallic phases formed in the Al/Fe reaction.

4:10 PM  Invited
Nanolaminated Structures in Metals Induced by Plastic Deformation with High Strain Rates and Strain Gradients: Xiaochun Liu1; Wei Xu1; Ke Lu1; 1Institute of Metal Research, Chinese Academy of Sciences
    Formation of high angle grain boundaries is believed to be the primary mechanism governing the strain-induced grain refinement in metals. With an increasing plastic strain, usually a steady-state microstructure with submicro-sized randomly-oriented grains is resulted as the mechanically-induced GB migration is activated. Recently surface mechanical grinding treatment (SMGT) was developed to induce high-rate shear deformation with very large strain gradient, with which nanolaminated (NL) structures with low angle grain boundaries (LAGBs) were fabricated in a number of metals. The boundary space ranges from a few nm to a few tens nm, about one order of magnitude smaller than the saturation structural sizes processed by conventional severe plastic deformation. In this talk, the structure characteristics and formation mechanisms of the NL structures will be presented. The effects of strain rates, strain gradients, and processing temperature on the extraordinary structural refinement will be discussed in several samples including pure metals and alloys.

4:30 PM  
Tailoring the Mechanical Properties of Nanolaminates Processed by Accumulative Roll Bonding: Mathias Göken1; Heinz Werner Höppel1; 1Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
     Laminated metal composites (LMCs) can be produced easily and in large quantities by the accumulative roll bonding process, where different metallic sheets are stacked and rolled together. The ARB-process allows to obtain so-called nanolaminates with layer thicknesses in the range of a few micrometers down to some tens of nanometers. With this approach many metallic materials can be combined to tailor and achieve optimum mechanical properties. The presentation will focus on the material combinations of Al and steels, Al and Ti, and Al and Cu, which are promising candidates to achieve interesting combinations of the mechanical properties and to gain a better understanding of the deformation mechanisms. The mechanical properties have been investigated in terms of strength, fatigue properties and influences from the local strain rate sensitivity by nanoindentation measurements. The achieved properties will be compared and discussed based on the chosen alloy system and stacking sequence of the sheets.

4:50 PM  Invited
The Development of Deformation Heterogeneity in Cu/Nb Lamellar Composites Predicted by Nonlocal Single Crystal Plasticity: Jason Mayeur1; Irene Beyerlein2; 1Los Alamos National Laboratory; 2University of California, Santa Barbara
    In this talk we present a computational study of the development of deformation heterogeneity in Cu/Nb multilayered lamellar composites produced by accumulative roll-bonding (ARB). ARB is a manufacturing process capable of producing bulk multilayered lamellar composites with layer thicknesses ranging from mm to nm. ARB lamellar composites are distinct from those produced by physical vapor deposition in terms of the specimen scale and layer thicknesses that are attainable as well as the predominant texture and heterophase interface character. Crystal plasticity simulations of multilayer statistical volume elements are performed to characterize the development of heterogeneities at the subgranular, granular, and layer scales. A nonlocal crystal plasticity constitutive framework is used in order to assess the role of lattice curvature and geometrically necessary dislocations on the evolution of the heterogeneous fields and comparisons are made to results obtained using a classical local theory.

5:15 PM  
Iron-aluminum Metallic-intermetallic Laminate (MIL) Composites: Haoren Wang1; Yu Wang2; Kenneth Vecchio1; 1University of California, San Diego; 2Dalian University of Technology
    Metallic-intermetallic laminate composites can be fabricated via hot pressing alternating stacked metal foils. The reactive sintering of dissimilar metals can form intermetallic compounds, which typically have high modulus and high hardness, but are often brittle. Tailoring the initial metal foil thickness, reaction temperature and time can produce laminate composites with alternating metallic and intermetallic layers, which combine ductility from residual metallic layers and stiffness from the intermetallic layers. Iron and aluminum are two of the lowest cost structural metals, so studying MIL composites in the iron-aluminum system may facilitate developing high-performance structure materials at low cost. Specifically, among various intermetallic compounds in the Fe-Al system, the FeAl phase (B2) has similar lattice structure with BCC-iron, and possesses the best mechanical properties of the intermetallic phases, making it an ideal intermetallic layer material. This presentation will demonstrate a processing path to the formation of Fe-FeAl MIL composites with unique mechanical performance.