Computational Thermodynamics and Kinetics: Solid-Liquid Transformations and Properties
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Computational Materials Science and Engineering Committee
Program Organizers: Nana Ofori-Opoku, Canadian Nuclear Laboratories; Jorge Munoz, University of Texas at El Paso; Sara Kadkhodaei, University Of Illinois Chicago; Vahid Attari, Texas A&M University; James Morris, Ames Laboratory
Tuesday 8:30 AM
February 25, 2020
Room: 33C
Location: San Diego Convention Ctr
Session Chair: Gilles Demange, University of Rouen; Nana Ofori-Opoku, Canadian Nuclear Laboratories
8:30 AM Invited
Phase-field Lattice Boltzmann Simulations of Dendrite Growth with Melt Flow: Tomohiro Takaki1; Shinji Sakane1; Munekazu Ohno2; Yasushi Shibuta3; 1Kyoto Institute of Technology; 2Hokkaido University; 3The University of Tokyo
Computer simulation of dendrite growth with melt flow remains a challenging issue in alloy solidification. In particular, simulations using the phase-field method, which is the most accurate dendrite prediction model, are the most challenging due to their large computational cost. We have been trying to resolve this problem by parallel GPU (graphics processing units) computing using a GPU supercomputer. In this talk, we introduce our previous and state‐of‐the‐art studies regarding phase-field simulations of dendrite growth with melt flow: Dendrite growth in forced [J. Cryst. Growth, 474 (2017) 154-159] and natural [J. Cryst. Growth, 474 (2017) 146-153] convections, permeability prediction [Acta Mater., 164 (2019) 237-249], dendrite growth with motion [Comput. Mater. Sci., 147 (2018) 124–131], introduction of adaptive mesh refinement, and so on.
9:00 AM
Thermodynamics and Kinetics of Electrochemical Solid/Liquid Interfaces: Role of the Solvent: Mira Todorova1; Suhyun Yoo1; Sudarsan Surendralal1; Joerg Neugebauer1; 1Max Planck Institut fur Eisenforschung
Processes at solid-liquid interfaces are at the heart of many present day technological challenges related to the improvement of battery materials, electro-catalysis, fuel cells, corrosion and others. Describing and quantifying the underlying fundamental mechanisms is equally challenging for experimental and theoretical techniques. Using the example of ZnO(0001) surfaces in aqueous environment we discuss how by combining density functional theory with thermodynamics we gain insight into the role the aqueous electrolyte plays in shaping surfaces [Phys. Rev. Lett. 120, 066101 (2018)]. Proceeding beyond the thermodynamic description, we utilize our novel potentiostat design to study reactions at electrochemical solid/liquid interfaces under controlled bias [Phys. Rev. Lett. 120, 246801 (2018)]. Focusing on one of the most corrosive system under wet corrosion, we solve a 150-year-old problem, which links H-evolution under anodic conditions to Mg dissolution.
9:20 AM Invited
Modeling Nucleation in the Phase-field and Phase-field Crystal Models: Tamás Pusztai1; Frigyes Podmaniczky1; Gyula Tóth2; László Gránásy1; 1Wigner Research Centre For Physics; 2Loughborough University
Solidification of an undercooled melt starts with the appearance of small solid particles that can grow further, a process called nucleation. Nucleation is initiated by the thermal fluctuations present in the melt. Modeling nucleation is a challenging task, because of its stochastic nature, the extremely small time and length scales involved, and its sensitivity on the process and model parameters, to name a few difficulties. Using the traditional phase-field and atomistic phase-field crystal models I introduce the techniques to describe nucleation by these methods and I show examples of simple and complex nucleation mechanisms, such as homogeneous, heterogeneous and athermal nucleation, phase selection via competing nucleation, amorphous precursor assisted nucleation of the crystalline phase, and the formation of orientational defects in the growing crystal via growth front nucleation.
9:50 AM
Molecular Dynamics Simulations of Heterogeneous Nucleation from Undercooled Melt: Fujinaga Takuya1; Yasushi Shibuta1; 1The University of Tokyo
Heterogeneous nucleation from undercooled melt is systematically investigated by molecular dynamics simulations. Firstly, athermal heterogeneous nucleation via grain refiners inoculated in undercooled Al melt is investigated. A thin solid Al layer appears on close-packed surfaces of a cubic Ti particle and it grows to a spherical cap consisting of FCC Al, whereas no cap structure appears on the other surfaces. There is a threshold undercooling temperature dividing growth modes between stagnation and free growth. Since threshold undercooling temperature is proportional to the inverse of effective particle radius, cap formation at the surface of the Ti particle is regarded as athermal heterogeneous nucleation. Next, the effect of anisotropy seed crystal on morphology of crystal is investigated for several FCC metals. Preferential growth toward specific orientation causes asymmetric crystal structure.
10:10 AM Break
10:30 AM Invited
Bridging Multi Scales for Predicting Structures and Properties in Solidification of Metals and Alloys: Mohsen Asle Zaeem1; 1Colorado School of Mines
High temperature processes of metals and alloys often involve solidification which controls the formation of defects and phases, and determines the overall nano/microstructures and properties of solidified products. Due to the multi length and time scale characteristics of solidification, we present a systematic multiscale modeling framework to study solidification. A procedure will be presented for developing accurate interatomic potentials capable of predicting high temperature properties and phases of several metals and alloys, including Al and Ti alloys. The interatomic potentials are developed based on the semi-empirical modified embedded atom method using low and high temperature data from electronic structure calculations and experiments. By utilizing large scale molecular dynamics (MD) simulations, the capabilities and transferability of these potentials are tested in study of the heterogeneous nucleation and phase formation processes during rapid solidification of metals and alloys. Employing MD results, we present quantitative phase-field models to accurately predict the solidification microstructures.
11:00 AM
Calculating the Eutectic Coupled Zone in a Ternary System via Genetic Optimization: George Lindemann1; Ashwin Shahani1; 1Department of Materials Science and Engineering, University of Michigan
Genetic algorithms (GA) are utilized, under a set of specific assumptions, to connect a model for growth in three-phase eutectic systems to the experimentally determined coupled zone for the Al-Ag-Cu ternary system. GA was used to deduce values for the various kinetic coefficients so as to minimize mismatch between the experimental coupled zone data and that of one mathematically derived. Sixteen different combinations of kinetic coefficients were found to accurately predict above 90% of the provided sample points for a set of growth velocity (V) and temperature gradient (G) measurements. For further validation, samples of varying V and G were prepared and characterized through correlative electron microscopy and 3D X-ray micro-tomography. Primary-phase, two phase, and three-phase eutectic microstructures were identified in the as-solidified samples then compared against the predictions of the derived model. It is anticipated that such a machine driven approach may find applicability in other areas of solidification science.