Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session P46: Metals III |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Michael Mehl, NRL Room: 311 |
Wednesday, March 16, 2016 2:30PM - 2:42PM |
P46.00001: ABSTRACT WITHDRAWN |
Wednesday, March 16, 2016 2:42PM - 2:54PM |
P46.00002: Orbital-free ab initio molecular dynamics study of the free liquid surface of Cd. Beatriz Gonzalez del Rio, Luis Enrique Gonzalez Tesedo We report results of an orbital-free \textit{ab initio} molecular dynamics (OF-AIMD) study of the free liquid surface of Cd at 800 K. A key ingredient in the OF-AIMD method is the local ionic pseudopotential describing the ions-valence electrons interaction. We have developed a force-matching method [1] to derive a local ionic pseudopotential suitable to account for a rapidly varying density system, such as a free liquid surface. Results are reported for several structural properties. The calculated reflectivity shows a marked maximum whose origin is related to the surface layering, along with a shoulder located at a much smaller wavevector transfer. \smallskip [1] B. G. del Rio and L. E. Gonzalez, J. Phys.: Condens. Matter \textbf{26}, 465102 (2014) [Preview Abstract] |
Wednesday, March 16, 2016 2:54PM - 3:06PM |
P46.00003: \textbf{A parametric study of surface roughness and bonding mechanisms of aluminum alloys with epoxies: a molecular dynamics simulation.} Rajendra Timilsina, Stephanie TerMaath The marine environment is highly aggressive towards most materials. However, aluminium-magnesium alloys (Al-Mg, specifically, 5xxx series) have exceptionally long service life in such aggressive marine environments. For instance, an Al-Mg alloy, AA5083, is extensively used in naval structures because of its good mechanical strength, formability, seawater corrosion resistance and weldability. However, bonding mechanisms of these alloys with epoxies in a rough surface environment are not fully understood yet. It requires a rigorous investigation at molecular or atomic levels. We performed a molecular dynamics simulation to study an adherend surface preparation and surface bonding mechanisms of Al-Mg alloy (AA5083) with different epoxies by developing several computer models. Various distributions of surface roughness are introduced in the models and performed molecular dynamics simulations. Formation of a beta phase (Al$_{\mathrm{3}}$Mg$_{\mathrm{2}})$, microstructures, bonding energies at the interface, bonding strengths and durability are investigated. [Preview Abstract] |
Wednesday, March 16, 2016 3:06PM - 3:18PM |
P46.00004: ABSTRACT WITHDRAWN |
Wednesday, March 16, 2016 3:18PM - 3:30PM |
P46.00005: Viscoelastic damping in crystalline composites and alloys Raghavan Ranganathan, Rahmi Ozisik, Pawel Keblinski We use molecular dynamics simulations to study viscoelastic behavior of model Lennard-Jones (LJ) crystalline composites subject to an oscillatory shear deformation. The two crystals, namely a soft and a stiff phase, individually show highly elastic behavior and a very small loss modulus. On the other hand, when the stiff phase is included within the soft matrix as a sphere, the composite exhibits significant viscoelastic damping and a large phase shift between stress and strain. In fact, the maximum loss modulus in these model composites was found to be about 20 times greater than that given by the theoretical Hashin-Shtrikman upper bound. We attribute this behavior to the fact that in composites shear strain is highly inhomogeneous and mostly accommodated by the soft phase, corroborated by frequency-dependent Gr\"{u}neisen parameter analysis. Interestingly, the frequency at which the damping is greatest scales with the microstructural length scale of the composite. Finally, a critical comparison between damping properties of these composites with ordered and disordered alloys and superlattice structures is made. [Preview Abstract] |
Wednesday, March 16, 2016 3:30PM - 3:42PM |
P46.00006: A general and predictive model of anisotropic grain boundary energy and morphology for polycrystal-level simulations Brandon Runnels, Irene Beyerlein, Sergio Conti, Michael Ortiz In this work, a new model for anisotropic GB energy and morphology is formulated that is fast, general, dependent on only three material parameters, and is verified by comparison with more than 40 MD and experimental datasets for (a)symmetric, tilt/twist, FCC/BCC materials, as well as experimental measurements. A relaxation algorithm is presented that is able to efficiently compute the optimal facet pattern and corresponding relaxed energy. Finally, the GB model is implemented as an interface model in a polycrystal simulation to observe the effects of GB in conjunction with elastic and plastic deformation. The simulations are compared with those using an isotropic GB model, and the effect of the GB isotropy on the bulk properties and microstructure is determined. The results have applications towards, e.g., improved polycrystal simulations, understanding void nucleation, and GB engineering. [Preview Abstract] |
Wednesday, March 16, 2016 3:42PM - 3:54PM |
P46.00007: Atomic-Scale Imprinting into Amorphous Metals Udo Schwarz, Rui Li, Georg Simon, Emely Kinser, Ze Liu, Zheng Chen, Chao Zhou, Jonathan Singer, Chinedum Osuji, Jan Schroers Nanoimprinting by thermoplastic forming (TPF) has attracted significant attention in recent years due to its promise of low-cost fabrication of nanostructured devices. Usually performed using polymers, amorphous metals have been identified as a material class that might be even better suited for nanoimprinting due to a combination of mechanical properties and processing ability. Commonly referred to as metallic glasses, their featureless atomic structure suggests that there may not be an intrinsic size limit to the material's ability to replicate a mold. To study this hypothesis, we demonstrate atomic-scale imprinting into amorphous metals by TPF under ambient conditions. Atomic step edges of a SrTiO$_{3}$ (STO) single crystal used as mold were successfully imprinted into Pt-based bulk metallic glasses (BMGs) with high fidelity. Terraces on the BMG replicas possess atomic smoothness with sub-Angstrom roughness that is identical to the one measured on the STO mold. Systematic studies revealed that the quality of the replica depends on the loading rate during imprinting, that the same mold can be used multiple times without degradation of mold or replicas, and that the atomic-scale features on as-imprinted BMG surfaces has impressive long-term stability (months). [Preview Abstract] |
Wednesday, March 16, 2016 3:54PM - 4:06PM |
P46.00008: First principles study of lattice disordering and magnetic behavior in CuNiMnAl and CuNiMnSn Heusler alloys Shifrah Aron-Dine, Gregory Pomrehn, Aurora Pribram-Jones, Lori Bassman In this work we present density functional theory calculations on two new Heusler alloys, CuNiMnAl and CuNiMnSn, and explore how the electronic properties of these structures are affected by atomic disordering. Elements are disordered 1{\%}-25{\%} on constant and varying sublattices to explore changes in electronic structure and magnetization. We then use a Monte Carlo method to predict expected magnetic behavior and compare with experimental results. [Preview Abstract] |
Wednesday, March 16, 2016 4:06PM - 4:18PM |
P46.00009: First principles statistical mechanics of alloys and magnetism Markus Eisenbach, Suffian N. Khan, Ying Wai Li Modern high performance computing resources are enabling the exploration of the statistical physics of phase spaces with increasing size and higher fidelity of the Hamiltonian of the systems. For selected systems, this now allows the combination of Density Functional based first principles calculations with classical Monte Carlo methods for parameter free, predictive thermodynamics of materials. We combine our locally selfconsistent real space multiple scattering method for solving the Kohn-Sham equation with Wang-Landau Monte-Carlo calculations (WL-LSMS). In the past we have applied this method to the calculation of Curie temperatures in magnetic materials. Here we will present direct calculations of the chemical order – disorder transitions in alloys. We present our calculated transition temperature for the chemical ordering in CuZn and the temperature dependence of the short-range order parameter and specific heat. Finally we will present the extension of the WL-LSMS method to magnetic alloys, thus allowing the investigation of the interplay of magnetism, structure and chemical order in ferrous alloys. [Preview Abstract] |
Wednesday, March 16, 2016 4:18PM - 4:30PM |
P46.00010: First-principles Co database: Energetics of binary Co alloys and compounds Shahab Naghavi, Vinay Hegde, Chris Wolverton The field of superalloys has received a recent spike in interest with the discovery of metastable $\gamma^{\,\prime}\!-$Co$_{3}$(Al,W) precipitates with the L1$_{2}$ structures. We present density functional calculations for the first and second nearest-neighbor solute-vacancy binding energies of 27 substitutional solutes in fcc-cobalt. As by-products, we also calculate the dilute mixing energy, dilute volume of mixing, and solubility enthalpy. A modest correlation between the solute size and its binding to an accompanying vacancy has been found. Our calculations reveal that a vacancy not only relieves the strain associated with large solutes, but also mediates a weak bonding between the large solute and its next nearest-neighbor atoms, resulting in high solute-vacancy binding energies. We also find that the solute-vacancy binding energy is minimized for a half-filled $d$-band, in the middle of a transition metal series, and varies parabolically with the $d$-band filling. In general, $4d$ and their counterpart $5d$ transition metals have nearly similar solute-vacancy binding energies, but much larger than those of $3d$ transition metals, and the deviation increase by moving away from a half-filled band. [Preview Abstract] |
Wednesday, March 16, 2016 4:30PM - 4:42PM |
P46.00011: X-ray measurements of the self-organization of martensitic variants during thermal cycling Daniel Perez, Mark Sutton, Michael Rogers The deformation of most types of metals involves an irreversible flow of crystallographic dislocations. This allows for their ductility. The deformation of a metallic shape memory alloy (SMA), on the other hand, is accommodated by a solid-solid phase transition. If deformed in the low-temperature martensitic phase, an SMA can be returned to its original shape by raising its temperature to the point where it changes back to its high-temperature parent phase. When the reverse occurs and the transformation is from parent to martensitic phase, an SMA goes from a high-symmetry to a low-symmetry state in which a number of martensitic variants are produced. We monitored the self-organization of these variants during cycles of periodic thermal driving. This was done using in situ X-ray Photon Correlation Scectroscopy (XPCS), which uses correlation from X-ray speckle to quantify the degree of microstructural change in a material. Our measurements revealed enhanced reversibility in the organization of the martensitic variants as the system evolved during repeated thermal cycling. [Preview Abstract] |
Wednesday, March 16, 2016 4:42PM - 4:54PM |
P46.00012: Long-time atomistic evolution of grain boundary in nickel using the kinetic activation-relaxation technique Sami Mahmoud, Mickaël Trochet, Oscar Restrepo, normand Mousseau The microscopic mechanisms associated with the evolution of metallic materials are still a matter of debate as both experimental and numerical approaches fail to provide a detailed atomic picture of their time evolution. Here, we use the kinetic activation-relaxation technique (k-ART) [1], an unbiased off-lattice kinetic Monte Carlo method with on-the-fly catalog building to overcome these limitations and follow the atomistic evolution of a 10.000-atom grain boundary Ni system over macroscopic time scales. We first characterize the kinetic properties of four different empirical potentials, the embedded atom method (EAM), the first and second modified embedded atom method (MEAM1NN and MEAM2NN respectively) and the Reax force field (ReaxFF) potentials. Comparing the energetics, the elastic effects and the diffusion mechanisms for systems with one to three vacancies and one to three self-interstitials in nickel simulated over second time scale, we conclude that ReaxFF and EAM potentials are closest to experimental values. We then proceed to study the long-time evolution of a grain boundary with the Reax forcefield and to offer a detailed description of its energy landscape, including the exact description of short and long-range effects on self-diffusion along the interface. [1] N. Mousseau \textit{et al}, \textit{Comput. Mater. Sci.}, vol. 100, pp. 111--123, 2015. [Preview Abstract] |
Wednesday, March 16, 2016 4:54PM - 5:06PM |
P46.00013: Fluid-like flows in large-strain deformation of metals Ho Yeung, Dinakar Sagapuram, Koushik Viswanathan, Narayan Sundaram, Anirban Mahato, Kevin Trumble, Srinivasan Chandrasekar Laminar or smooth plastic flow, commonly observed in large deformation of metals, becomes unstable under certain conditions, resulting in inhomogeneous plastic flow. Using \emph{in situ} imaging, we demonstrate the unique features of two inhomogeneous flow modes in metal plasticity --- the well-known shear band flow and the recently discovered sinuous flow --- and methods for suppressing them. Both modes occur via a two stage process --- nucleation and flow development. The nucleation stage results in a weak material zone and the development stage involves imposition of significant strains. In the case of shear bands, using additional micro-marker techniques, we show that the second stage is well described by a viscous slider model. As a result, controlling the second stage causes band formation to cease. We demonstrate the use of this method --- Passive Geometric Flow control --- to form long strips from metallic alloys that are difficult to form conventionally. For sinuous flow, nucleation and flow formation kinematics show remarkable resemblance with flows in complex fluids. The nucleation stage can be altered using suitable ink coatings on the free surface or by surface pre-straining, and we use this idea to demonstrate complete sinuous flow suppression. [Preview Abstract] |
Wednesday, March 16, 2016 5:06PM - 5:18PM |
P46.00014: Grain Growth in Cerium Metal Jason Cooley, Martha Katz, Charles Mielke, Joel Montalvo We report on grain growth in forged and rolled cerium plate for temperatures from 350 to 700 degrees C and times from 30 to 120 minutes. The cerium was made by arc-melting into a 25 mm deep by 80 mm diameter copper mold. The resulting disk was forged at room temperature to a 25{\%} reduction of thickness four times with a 350 degree C strain relief heat treatment for 60 minutes between forging steps. The resulting 8 mm thick plate was clock rolled at room temperature to a 25{\%} reduction of thickness three times with a 350 C strain relief heat treatment between steps resulting in a plate approximately 3 mm thick. 5 x 10 mm coupons were cut from the plate for the grain growth study. [Preview Abstract] |
Wednesday, March 16, 2016 5:18PM - 5:30PM |
P46.00015: Ab initio calculation of oxygen self-diffusion coefficient in uranium dioxide UO$_{2}$ Boris Dorado, Philippe Garcia, Marc Torrent Uranium dioxide UO$_{2}$ is the most widely used nuclear fuel worldwide and its atomic transport properties are relevant to practically all engineering aspects of the material. Although transport properties have already been studied in UO$_{2}$ by means of first-principles calculations, the ab initio determination of self-diffusion coefficients has up to now remained unreachable because the relevant computational tools were neither available or adapted. The present work reports our results related to the ab initio calculation of the oxygen self-diffusion coefficient in UO$_{2}$. We first determine the Gibbs free energies of formation of oxygen charged defects by calculating both the electronic and vibrational (hence entropic) contributions. Then, we use the transition state theory in order to compute the effective jump frequency of the defects, which in turn provides us with the value of the pre-exponential factor. The results are compared to self-diffusion data obtained experimentally with a careful monitoring of the relevant thermodynamic conditions (oxygen partial pressure, temperature, impurity content). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700