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Computational Thermodynamics and Kinetics: Process Modeling and Thermodynamics
Sponsored by: TMS Functional Materials Division, TMS Materials Processing and Manufacturing Division, TMS: Chemistry and Physics of Materials Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Integrated Computational Materials Engineering Committee, TMS: Solidification Committee
Program Organizers: Hesam Askari, University Of Rochester; Damien Tourret, IMDEA Materials Institute; Eva Zarkadoula, Oak Ridge National Laboratory; Enrique Martinez Saez, Clemson University; Frederic Soisson, Cea Saclay; Fadi Abdeljawad, Lehigh University; Ziyong Hou, Chongqing University

Wednesday 8:30 AM
March 22, 2023
Room: 26A
Location: SDCC

Session Chair: Hesam Askari, University Of Rochester; Naga Sri Harsha Gunda, The Ohio State University

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8:30 AM  Invited
Effective Temperature Concept for Steady States in Driven Alloy Systems: Pascal Bellon¹; Robert Averback¹; Sourav Das¹; ¹University of Illinois at Urbana-Champaign
    Alloys driven by external forcing such as irradiation and plastic deformation are often observed to reach steady states. In the case of immiscible elements, the resulting steady-state solubility measured in experiments can be rationalized by an effective temperature, which is a measure of the configurational entropy of steady-state microstructures. At low physical temperature, irradiation and deformation stabilize solid solutions and this effective temperature is thus infinite. In high immiscible and highly reactive systems, however, irradiation and severe plastic deformation are found to trigger decomposition even at physical temperatures so low that thermal activated migration of point defects and solute is suppressed. Using atomistic modeling it is shown that a finite effective temperature, designated as the process temperature, can be introduced to capture such decomposition reactions at low physical temperatures. A parallel is made with the effective temperature introduced in the thermodynamic dislocation theory for steady-state dislocation density in deformed crystals.

9:00 AM  
Energy: a Path Forward to Connect Radiation Damage Simulations and Experiments: Charles Hirst¹; Rachel Connick¹; Penghui Cao²; R. Scott Kemp¹; Michael Short¹; ¹Massachusetts Institute of Technology; ²University of California Irvine
    Experimentally validating decades of radiation damage simulations remains an outstanding challenge for the field of nuclear materials science. Current characterisation techniques are unable to detect the full spectrum of defects in irradiated metals. We propose to overcome this challenge by characterising defects through their energetic signatures of activation and annihilation, upon heating. Molecular dynamics annealing simulations are used to predict the stored energy release of Al electron-irradiated at cryogenic temperatures. Extrapolation across 11 orders of magnitude in time and 18 orders of magnitude in mass yields results which match previous experiments within a factor of 2. These results are used to evaluate the combination of material parameters which generate statistically-significant measurements of stored energy release in irradiated materials. This work demonstrates the power of simulated and experimental defect annealing, and reveals a new route between modelling and measurement in materials science.

9:20 AM  
An Efficient and Accurate Linear Spline Interpolation Method of Implementing CALPHAD Thermodynamics in Phase Field Models: Kartikey Joshi¹; Siu Sin Jerry Quek¹; Yingzhi Zeng¹; David Wu¹; ¹Institute of High Performance Computing
     In phase field models for phase transformations in alloys, the composition and temperature dependent Gibbs free energy G^p(x_i^p,x_j^p…,T) of constituent phases are commonly expressed in terms of auxiliary composition fields (x_i^p), which denote the concentration of a particular solute (x_i) in a constituent phase p, with the following constraints: (1) x_i= ∑_p=1^Nh_px_i^p; (2) ∂G^p/∂x_i^p=∂G^q/∂x_i^q,where h_p denotes the volume fraction of phase p at a point and (2) describes the condition for quasi-equilibrium between constituent phases p and q. In this work, we discretize the composition space with elements having linear shape function to express the free energy as linear function of composition, allowing us to obtain accurate solutions of the auxiliary composition fields (1) and (2) more efficiently than Redlich-Kister polynomials-based method. We also show via phase field simulations that the proposed approach is significantly more accurate than using a parabolic approximation of the free energy.

9:40 AM  
Development of Continuous Cluster Activation Method and Its Application to Grain Growth: Ryo Yamada¹; Munekazu Ohno¹; ¹Hokkaido University
    Atomistic behavior in metals and alloys have been broadly investigated using molecular dynamics (MD) simulation. The applicability of MD simulation, however, is limited to a phenomenon at relatively small time scale because of its large computational burden. Recently, phase-field crystal (PFC) method has attracted lots of attentions because it can simulate atomistic behaviors at diffusive time scale. The PFC method is versatile, and a variety of phenomena have been simulated. However, it is basically a phenomenological approach, and a determination of input parameters in PFC method is not an easy task, which limits the applicability. In this work, a new atomistic simulation model is proposed, which is an extension of cluster activation method (CAM) from discrete to continuous spaces (so-called continuous CAM) and uses interatomic interaction energies as its main input parameters. This statistical mechanics based approach is applied to a grain growth behavior, and its reliability is discussed.

10:00 AM Break

10:20 AM  
Significance of Free Energy Contributions beyond Configurational Entropy in Superalloys and High Entropy Alloys: Naga Sri Harsha Gunda¹; Maryam Ghazisaeidi¹; ¹The Ohio State University
    Configurational entropy plays a vital role in stabilizing high entropy alloys and multi-component superalloys with a superior mechanical response. However, alloy design requires accurate determination of free energies in competing disordered systems such as fcc- and hcp-based solid solutions. The derivation of entropies beyond configurational entropy is not well established for systems with complex compositions. We present a methodology using first-principles calculations to derive the necessary contributions to the free energy for accurately determining relative stability between phases at finite temperatures. We show the significance of calculating entropy from vibrations, electronic excitations, and magnetism to determine phase transformation temperatures in the NiCoCr ternary derivative of cantor alloy. Here the hcp disordered phase is expected to be stable at lower temperatures. Furthermore, we will demonstrate the competing phase stability in fcc Ni-based superalloys where the localized phase transformation phenomenon stabilized the hcp phase.

10:40 AM  
Assessment of Spinodal Decomposition in Cr-W Based Smart and High-entropy Alloys from First-principles Modelling: Duc Nguyen-Manh¹; Jan Wrobel²; Damian Sobieraj²; ¹UK Atomic Energy Authority; ²Warsaw University of Technology
    Self-passivating Metal Alloys (W-Cr-Y-Zr) with Reduced Thermo-oxidation (SMART) and High-Entropy Alloys (HEA) W-Cr-V-Ta with outstanding radiation resistance are under development as plasma-facing materials for the future fusion power plants. The phase stability and short-range order (SRO) of these alloys has been investigated, using a combination of Density Functional Theory and Cluster Expansion methods and Monte-Carlo simulations using thermodynamic integration method. It is found that alloying Zr into SMART W alloys increases the temperature of spinodal decomposition between W and Cr in a comparison with those investigated previously for W-Cr-Y alloys. The chemical SRO between Y-Zr is predicted to be strongly negative leading to the co-segregation of these elements. For the high concentrated HEAs, the competition between spinodal decomposition and radiation effects is discussed in term of free energies and W-Cr SRO computed as a function of temperature and alloy compositions and in a comparison with experimental observations of radiation-induced segregation.

11:00 AM  Invited
Data-driven Models of Plasticity and Thermodynamics: Discrete and Continuous State Spaces: Thomas Swinburne¹; ¹CNRS CRCN, Aix-Marseille University
    Building models for the plasticity, thermodynamics and kinetics of metals is challenging as subtle aspects of atomic cohesion must be faithfully reproduced, and predictions often require averaging over large, complex configuration ensembles. I will discuss how the energy landscapes of atomic systems can be rapidly explored at scale and "coarse-grained" when the dynamics are thermally activated[1,2] and how data-driven techniques, typically used to regress energies for modern cohesive models, can be used to capture a much wider range of properties such as defect entropics[3] or dislocation properties[4]. When the dynamics are not clearly thermally activated, coarse graining is much more challenging. I will discuss how a data-driven approach can provide a solution, producing efficient surrogate models which can predict the evolution of nanoparticle ensembles and the yielding of complex microstructures, offering new perspectives for multiscale modelling approaches[5]. [1] TDS and D Perez, NPJ Comp. Mat 2020 [2] TDS and DJ Wales JCTC 2020 [3] C Lapointe et al. PRMat 2022 [4] P Griorev et al., Acta Materialia 2023 [5] TDS, In Prep

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