Computational Thermodynamics and Kinetics: Diffusion, Kinetics and Non-equilbrium Events
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Chemistry and Physics of Materials Committee, TMS: Computational Materials Science and Engineering Committee
Program Organizers: Nana Ofori-Opoku, Canadian Nuclear Laboratories; Eva Zarkadoula, Oak Ridge National Laboratory; Enrique Martinez Saez, Clemson University; Vahid Attari, Texas A&M University; Jorge Munoz, University of Texas at El Paso
Monday 2:00 PM
March 15, 2021
Room: RM 54
Location: TMS2021 Virtual
Session Chair: Pascal Bellon, University of Illinois at Urbana-Champaign; Enrique Martinez Saez, Clemson University; Nana Ofori-Opoku, Canadian Nuclear Laboratories; Maylise Nastar, C.E.A
2:00 PM
Hydrogen Diffusion and Trapping in Multiphase Materials: A Multiscale Model for Non-point Trapping: Fernando León Cázares1; Dominic Dziedzic1; Enrique Galindo-Nava1; 1University of Cambridge
Hydrogen embrittlement is a major degrading phenomenon in numerous structural alloys. A key issue to anticipate such behaviour is to predict the role of the microstructure on the hydrogen kinetics within the lattice. However, most diffusion models typically assume all defects to be point traps, which falls short in describing the effects of microstructural features such as secondary phases. In this work, hydrogen charging and thermal desorption spectroscopy are explored in duplex steels with varied austenitic contents to investigate the trapping effects of this phase. The behaviours are reproduced with a novel model for hydrogen diffusion in multiphase alloys that combines continuum diffusion laws at two different length scales. Parametric analyses yield clear size and volume fraction effects, which are then used to explain the behaviours of typical retained austenite morphologies in steels. An additional equilibrium model for volumetric phases and the regimes where this is valid are further discussed.
2:20 PM
Kinetic Assessment of HCP Mg-Li-Al Alloys: David Christianson1; Lilong Zhu2; Michele Manuel1; 1University of Florida; 2Yantai University
Mg-Li-Al alloys show great promise for light-weight rigid structures. However, a lack of kinetic descriptions for this system limits the capabilities of computational materials design. This work focuses on the development of a kinetic mobility database for the HCP Mg-Li-Al system using the CALPHAD method. Experimental diffusion analysis was performed using the diffusion couple process. A novel approach was taken to characterize Li diffusion profiles using a combination of Auger electron spectroscopy and inductively coupled plasma optical emission spectroscopy. Al diffusion profiles were acquired using electron probe microanalysis. The forward-simulation method was utilized to extract diffusion coefficients from experimental diffusion profiles. Mobility parameters were then optimized using the Thermo-Calc diffusion module, Diffusion Controlled TRAnsformations (DICTRA). The established mobility database was validated through comparing experimental and simulated diffusion profiles.
2:40 PM
Quantitative Inference of the Mobility Coefficient in the Cahn-Hilliard Equation from a Model Experiment: Zirui Mao1; Michael Demkowicz1; 1Texas A&M University
A common challenge in phase-field modeling using the Cahn-Hilliard equation is the determination of the mobility coefficient, which controls the kinetics of microstructure evolution. We propose an approach for inferring the mobility coefficient from a simple model experiment. We find that the product of mobility and the coefficient of the uniform free-energy term may be inferred uniquely based on three quantities that may be measured experimentally from the microstructure evolution of the proposed model experiment. If the free energy coefficient is determined by other means (e.g., form thermodynamic models), then the mobility may be calculated, as well. We conclude with a discussion of ongoing efforts to carry out the proposed model experiment.
3:00 PM Invited
Defect Kinetics in Multi-component Oxides via Accelerated Molecular Dynamics: Blas Uberuaga1; Ghanshyam Pilania1; 1Los Alamos National Laboratory
Understanding the kinetics of defects is critical for both describing and ultimately predicting the behavior of materials in many contexts, from advanced applications to their response to extreme conditions. While computational methods such as the nudged elastic band exist to calculate the relevant kinetic parameters for simple processes, in many systems the landscape is simply too complex to reduce to isolated unit processes. Materials such as spinels and pyrochlores feature multiple elements on the cation sublattices that can be arranged in multiple ways. Here, we use accelerated molecular dynamics to explore the kinetics of defects in these systems as a function of the cation ordering. We examine both the elemental processes but also how those add up to lead to net migration through the material. We contrast the behavior in spinels with other complex oxides to provide some generic insight regarding how cation ordering impacts defect transport in these systems.
3:30 PM Invited
Predicting Non-equilibrium Patterns Beyond Thermodynamic Concepts: Application to Radiation Induced Microstructures: David Simeone1; Philippe Garcia1; Laurence Luneville1; 1CEA
In this work, we derive an analytical model to predict the appearance of all possible radiation-induced steady states and their associated microstructures in immiscible A(1-x)Bx alloys, an example of a non equilibrium dynamical system. This model is assessed against numerical simulations and experimental results which show that different microstructures characterized by the patterning of A-rich precipitates can emerge under irradiation. We demonstrate that the steady-state microstructure is governed by irradiation conditions but also by the average initial concentration of the alloy x. Such a dependence offers new leverage for tailoring materials with specific microstructures overcoming limitations imposed by the equilibrium thermodynamic phase diagram.
4:00 PM
Quantitative Phase-field Modeling for Corrosion of
Engine Materials at High Temperature: Xueyang Bognarova1; Michael Tonks1; 1University of Florida
The stainless steel (SS) valve materials in an internal combustion engine (ICE) environment can undergo microstructural evolution that sensitizes the material to corrosion and fatigue. The industry currently employs a conservative material selection approach that usually results in over-design and increased cost. The goal of this work is to develop a mesoscale phase-field simulation tool that investigates the corrosion mechanism of SS corrosion in an ICE, and determines the microstructural sensitive corrosion rate. With different ions diffusing in the oxide, charge neutrality and coupled current conditions are assumed to simulate how the electric potential affects diffusion and phase transformation. Strain energy induced during corrosion is coupled into the total energy functional and the stress divergence equation is solved. The phase-field model is implemented using the Multiphysics Object Oriented Simulation Environment (MOOSE), an open-source finite-element framework. The predicted corrosion rate has been verified against analytical models and validated against experimental data.
4:20 PM Invited
Molecular Dynamics Modeling of Embrittlement in Irradiated Nickel-base Alloys: Michael Demkowicz1; 1Texas A&M University
Nickel(Ni)-base alloys used in nuclear energy applications experience several forms of radiation damage, including displacement damage as well as formation of helium (He) impurities through transmutation reactions. As a result, these materials become embrittled. Molecular dynamics (MD) simulations are increasingly able to capture the atomic-scale mechanism responsible for this embrittlement. I will present recent work on MD modeling of crack initiation and propagation in Ni. The effect of different forms of radiation damage (defect clusters, He bubbles) as well as various microstructural elements (grain boundaries, slip bands) on embrittlement will be described. Prospects for direct comparisons between MD simulations of fracture and experimental investigations will be discussed.
4:50 PM Invited
Modeling Delayed-onset Kinetics of Materials Used in Nuclear Power Applications Using Atomistic Simulations: Laurent Karim Béland1; Cong Dai2; Peyman Saidi1; Eric Nicholson3; Yu Luo1; Chandra Singh3; Mark Daymond1; Zhongwen Yao1; 1Queen's University; 2Canadian Nuclear Laboratories; 3University of Toronto
Numerous effects of neutron irradiation on structural materials are characterized by an incubation period. Two such examples include breakaway irradiation-induced growth in Zr alloys and irradiation-induced dissolution of Ni(3)Al precipitates in X-750 alloys. In Zr, a minimal dose must be applied before observing breakaway growth. In X-750, an order-disorder transition is observed after a critical dose is applied; notably, this dose depends on temperature and He content.We present atomistic simulations that capture the delayed-onset kinetics characterizing both these processes. In Zr, we show collision cascades overlapping with prismatic vacancy loops present in high-enough density can initiate transformation of prismatic loops into basal loops, enabling break-away growth. In X-750, we combine density functional theory, molecular dynamics, the Activation Relaxation Technique nouveau, and rate-theory in order to predict the effect of temperature and He on the order-disorder transition in neutron-irradiated X-750. Surprinsingly, the presence of He delays the order-disorder transition.