Integration between Modeling and Experiments for Crystalline Metals: From Atomistic to Macroscopic Scales: Poster Session
Program Organizers: M Arul Kumar, Los Alamos National Laboratory; Irene Beyerlein, University of California, Santa Barbara; Levente Balogh, Queen's University; Josh Kacher, Georgia Institute of Technology; Caizhi Zhou, Missouri University of Science and Technology; Lei Cao, University of Nevada, Reno

Tuesday 11:00 AM
October 1, 2019
Room: Exhibit Hall CD
Location: Oregon Convention Center

P1-72: A Study on Finite Deformation of Copper Crystals Using the Principles of Crystal Plasticity: Experiments and Simulations: Suman Paik1; Bijan K Dutta2; Durgaprasad P V1; 1Bhabha Atomic Research Centre; 2Homi Bhabha National Institute
    The purpose of the present study is to investigate the room temperature deformation responses of high purity copper crystals both experimentally and numerically. At first, copper single crystals were fabricated and subjected to uniaxial compression loading at quasi-static strain rate. The stress-strain responses of copper single crystals along two crystallographic orientations were then extracted. Experimental results were complemented by conducting finite element simulations within a crystal plasticity framework by incorporating non-Schmid effects assuming cross-slip plays an important role on orientation dependence of the material. Finally, the macroscopic shape changes of deformed crystals were examined in detail.

P1-73: Atomic Simulation of Dynamic Recrystallization Initiated by Direct Grain Reorientation at High-angle Grain Boundary in Alpha-titanium: Hao Wang1; 1Institute of Metal Research
    Employing atomic-scale simulations, the response of a high-angle grain boundary, the soft/hard grain boundary, against external loading was systematically investigated. Under tensile loading close to the hard orientation, strain-induced dynamic recrystalliza-tion was observed to initiate through direct soft-to-hard grain reorientation, which was triggered by stress mismatch, inhibited by surface tension from the soft-hard grain boundary, and proceeded via interface ledges. Such grain reorientation corresponds with expansion and contraction of the hard grain along and perpendicular to the loading direction, respectively, accompanied by local atomic shuffling, providing relatively large normal strain of 8.3% with activation energy of 0.04 eV per atom. Tensile strain and residual dislocations on the hard/soft grain boundary facilitate the initiation of dynamic recrystallization by lowering the energy barrier and the critical stress for grain reorienta-tion, respectively.

P1-74: Crystal Plasticity Finite Element Analysis of Commercially Pure Titanium: Ji Hoon Kim1; Hye In Jung1; Joo-Hee Kang2; Chang-seok Oh2; 1Pusan National University; 2Korea Institute of Materials Science
    Commercially pure titanium having hexagonal close-packed structure exhibits unusual anisotropy and asymmetry at room temperature. Activation of various slip and twin modes during deformation is known to cause the complex deformation behaviour of commercially pure titanium. In order to examine the mechanical behaviour of commercially pure titanium, representative volume elements of the titanium were generated using the statistical data of the microstructure and the crystal plasticity finite element analysis was performed. The material parameters for the crystal plasticity model were calibrated using the macroscopic behaviour under various loading conditions. Yield point phenomena and the asymmetric hardening behaviour were analysed using the developed model.

P1-75: Diffuse-interface Approach to Modeling Plasticity, Interfacial Sliding and Coherency Loss: Tianle Cheng1; Youhai Wen1; Jeffrey Hawk1; 1US DOE, National Energy Technology Laboratory
    Structural materials applied at high temperatures often undergo creep deformation that involves plasticity and interfacial sliding. In precipitation hardened alloys, during aging the precipitates coarsen and then gradually lose coherency with the matrix. These processes and their interplay can significantly affect the macroscopic material performance. Here we develop a mesoscale modeling framework in which variational method is used to minimize the system free energy with respect to the inelastic eigenstrain associated with plastic as well as interfacial eigenstrains. The approach makes it feasible to fully couple plasticity and interfacial sliding with microstructure evolution within a Ginzburg-Landau framework. Numerical examples will be shown regarding polycrystal plasticity, grain boundary sliding and coherency loss.

P1-76: Evaluation of Van Der Waals Interactions in Uranium Phases using Density-functional Theory (DFT) using the Exchange-hole Dipole Moment (XDM) Dispersion Correction: Matthew Christian1; Erin Johnson2; Theodore Besmann2; 1University of South Carolina; 2Dalhousie University
    Density-functional theory (DFT) is a powerful tool to investigate properties of nuclear materials. However, there are unique challenges to modeling nuclear materials due to the complex electronic structure of actinide and lanthanide elements. Conventional DFT functionals lack the long-range, non-local correlation needed to calculate dispersion interactions, but they can be accounted for by adding a correction to the DFT energy. However, many DFT studies of nuclear materials neglect the inclusion of van der Waals interactions because they are assumed to marginally affect both structure and energies. In this work, we present a study of several uranium containing compounds (e.g., U, UCl3, UF3, UO2, USi3, U3Si) using DFT, incorporating the exchange-hole dipole moment (XDM) dispersion model. Our results will show how incorporating a dispersion correction affects crystal structure and Hubbard U parameter. The results will be compared to experimental values where available.

P1-77: Interface Formation during FCO to BCC Phase Transformation: Yipeng Gao1; Yongfeng Zhang1; Benjamin Beeler1; Bei Ye2; 1Idaho National Laboratory; 2Argonne National Laboratory
    Solid-solid phase transformation in crystalline solids may involve degenerate pathways, possibly leading to symmetry breaking. In consequence, diversified types of defects such as interfaces and dislocations can be generated in the product phase. One such example is the phase transformation between α (face-centered-orthorhombic, fco) and γ (body-centered-cubic, bcc) phases in uranium alloys, e.g., UZr and UMo alloys, in which reversible transformation has been widely observed. However, the possible defect generation during such reversible transformation has not been studied, and it is critical for the performance of those alloys as fuels in nuclear reactors. By utilizing advanced crystallographic tools, i.e., group theory and graph theory, we analyze the symmetry breaking during the α to γ phase transformation and its relationship with transformation-induced defects. A new defect generation mechanism is predicted by the theoretical analysis. The prediction is consistent with molecular dynamics simulations of phase transformation in U metal and experimental observations.

P1-78: Linking Microscale Experiments and Modeling to Predict Macroscale Mechanical Properties in Iron: Allyssa Bateman1; Geeta Monpara2; Ray Fertig2; Yaqiao Wu1; Brian Jaques1; 1Boise State University; 2University of Wyoming
    When paired with modeling, microscale mechanical testing can be used to predict bulk mechanical behavior, specifically in fields where a small sample size is optimal but knowledge of bulk mechanical properties is important. This study compared push-to-pull (PTP) microscale tensile tests to a single crystal plasticity model as a foundational work for relating microscale to bulk mechanical properties in iron alloys. Microscale iron tensile specimens were fabricated and mounted to PTP devices using a focused ion beam. This fixturing allowed for in-situ uniaxial tensile testing with a picoindenter in a transmission electron microscope. A single crystal plasticity model for body centered cubic (BCC) iron simulated the experimental design and was compared to tensile data extracted from the experiments. The simulation was performed in Multiphysics Object-Oriented Simulation Environment (MOOSE Framework). Results demonstrate the capability to replicate microscale experimental results with modeling and present a path forward for predicting bulk mechanical properties.

P1-79: Microstructural Evolution Simulation for Property Prediction in Solid State Additive Manufacturing: Danielle Cote1; Chris Massar1; Bryer Sousa1; Kyle Tsaknopoulos1; Victor Champagne2; 1Worcester Polytechnic Institute; 2U.S. Army Research Laboratory
    In solid state powder additive manufacturing processes, there is a direct correlation between the feedstock powder properties and the consolidated material and mechanical properties. To account for this relationship, a multi-scale through-process model was developed as a predictive tool to follow the microstructural evolution from as-received powder, powder treatment, consolidation, and post-processing. Since the thermodynamic and kinetic behavior varies significantly between powder and traditional wrought/cast metals, experimental analysis was used to calibrate these models for the powder. Both models and characterization cross length scales, from nanoscale powder microstructure to consolidation finite element simulations at the continuum scale. Extensive experimental characterization was required to calibrate and validate simulations, from HR-STEM and in-situ TEM to nanoindentation to macroscale mechanical property testing.

P1-80: Modeling Temperature-Dependent Yield Stress of FCC High-Entropy Alloys with Experimental Validation: Zongrui Pei1; Martin Detrois1; Paul Jablonski1; Jeffrey Hawk1; Ímer Doğan1; David Alman1; Michael Gao1; 1National Energy Technology Laboratory
    It is known that addition of molybdenum to steels and nickel-base alloys can increase the mechanical strength and the resistance to pitting corrosion. In this work, multi-scale computational modeling is carried out first to predict the temperature-dependent yield stress of a series of benchmark Co-Cr-Fe-Ni-Mo alloys. The modeling combines dislocation theory, first-principles density functional theory calculations, and hybrid Monte Carlo/molecular dynamics simulations. Ingots (~15 lb) were cast using vacuum induction melting followed by homogenization and thermal-mechanical processing. Reasonable agreement with experimental results on the benchmark alloys are obtained. Finally, high-throughput screening that integrates mechanical simulations and CALPHAD calculations is implemented to identify new cost-effective high-performance high entropy alloys that may hold promise for extreme environment applications such as high temperature, high pressure, and corrosion.

P1-84: Phase Field Modeling of the Influence of Thermo-mechanical Conditions on Phase Transformation in Titanium Alloys: Arun Baskaran1; Daniel Lewis1; 1Rensselaer Polytechnic Institute
    A multi phase field model is developed to study the influence of thermo-mechanical processing conditions on the solid state phase transformation in titanium alloys. A quantitative framework is adopted by coupling the phase field model to realistic thermodynamic and kinetic databases. Towards the goal of understanding the origins of different morphologies, the alpha-variant selection is modeled through the incorporation of local and non-local strain terms, such as misfit strain and transformation eigenstrain, under the formalism of micro-elasticity theory. A comparative study of classical and non-classical nucleation methods is performed, and the growth kinetics of the nuclei are analysed for different undercoolings, external stress, and overall solute compositions. We report the work in progress towards modeling the influence of processing conditions, such as cooling rate, and material history, such as prior-beta grain size, on microstructural evolution, and comparison of these results with the experimental observations on the alloy Ti-6Al-4V.

PI-86: Particle Effect on the Behavior and Spreading Kinetics of a Nano-suspension Drop: MD Simulations: Baiou Shi1; Weizhou Zhou2; Edmund Webb2; 1Penn State Erie; 2Lehigh University
    Nanosuspension has garnered tremendous attention recently in advanced material processing. The concept of assembling ordered arrays of nanoparticles on a substrate surface via suspension droplet wetting and subsequent evaporation has fueled a large body of research in this area. Self-pinning is a phenomenon intrinsic to the advancement or retraction of liquid/solid/vapor three-phase contact lines for nano-fluid droplets. Another relevant phenomenon is de-pinning, where an initially halted contact line separates from the pinning particle and continues its advance (or retraction) across the surface. Herein, results from molecular dynamics simulations will be presented to explore the particle effects during both pinning and de-pinning events. Results presented illustrate how particle size and concentration affects spreading kinetics and how this connects to dynamic droplet morphology and relevant forces that exist nearby the contact line region. Furthermore, wetting kinetics varies dramatically by tuning the interaction strength between the entrained particles and the underlying substrate.