Computational Thermodynamics and Kinetics: Software Tools and Material Prediction / Thermodynamics and Phase Selection
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

Tuesday 8:30 AM
March 16, 2021
Room: RM 54
Location: TMS2021 Virtual

Session Chair: Prashant Singh, Ames Laboratory; Vahid Attari, Texas A&M University; Enrique Martinez Saez, Clemson University; Carelyn Campbell, National Institute of Standards and Technology


8:30 AM  Invited
Application of CALPHAD-based Tools for Optimizing AM Microstructures and Properties: Carelyn Campbell1; Mark Stoudt1; James Zuback1; Souzan Hammadi2; 1National Institute of Standards and Technology; 2Royal Institute of Technology (KTH)
    While the rapid solidification, multiple heating and cooling cycles, and feedstock composition variations that occur during additive manufacturing (AM) processing generate unexpected microstructures and properties, these variations also provide opportunities both for the design of new alloys and for the optimization of existing alloys for AM processes. Several CALPHAD modeling tools can be utilized to optimize post-build processing and thereby tailor AM components to meet specific performance requirements. CALPHAD-based models are used to optimize the strength of AM martensitic stainless steels by limiting the solubility of nitrogen in the initial feedstock and by controlling the Cr/Ni ratio to achieve specific martensite lath microstructures. Post-build heat treatments are optimized using precipitation simulations to optimize the strengthening precipitates (Cu and Nb carbides and carbonitrides). The aqueous corrosion resistance can be qualitatively evaluated and optimized through comparison of multicomponent potential/pH diagrams to those of a wrought alloy composition.

9:00 AM  
Ga-Sn-Zn Alloys – Thermophysical Properties of Novel Liquid Metals: Alexandra Dobosz1; Tomasz Gancarz1; 1Institute of Metallurgy and Materials Science Polish Academy of Sciences
     Liquid metals are new functional materials that are being studied for a number of applications, including soft electronics [1], medicine [2], and thermal management of various systems [3]. In the case of any of those applications the thermophysical properties of the materials have to be assessed. We propose the use of non-toxic Ga-Sn-Zn alloys. Based on thermodynamic assessment, the density, viscosity and surface tension has been calculated via different models, including the Egry model for density, Sato, Kucharski, Moelywen-Hughes, Kozlov, Romanov and Petrov, Schick and Gasior models in the case of viscosity and Kohler, Toop, Muggiano and Butler models for surface tension. Experiments performed using the discharge crucible method are in good agreement with the models. [1] Dickey, M.D, Advanced Materials, 29 (2017) 1606425. [2] Yan, J. et al., Chemical Society Reviews 47 (2018) 2518-2533.[3] Gao, Y. et al., Applied Physics A 107 (2012) 701-708.

9:20 AM  Invited
Understanding Phase Stability and Diffusion Kinetics in Structurally Unstable Phases from First-principles: Sara Kadkhodaei1; 1University of Illinois at Chicago
    The phase diagram of numerous materials of technological importance features high temperature phases that exhibit phonon instabilities. Leading examples include shape-memory alloys, ferroelectric, refractory, and structural materials. In this talk I will introduce a new thermodynamic model for free energy calculation in these phases from first principles. This model efficiently explores the system’s ab-initio energy surface by partitioning it into piecewise polynomials around local minima, which is combined with a continuous yet constrained sampling in the vicinity of these local minima. I present the application of this model to the bcc phase of titanium as well as the austenite and martensite phases in NiTi and PtTi shape memory alloys. In addition, I will try to shed light on diffusion kinetics in dynamically stabilized phases based on a first-principles approach within the transition state theory. Finally, I introduce the implementation of the model as an open-access and fully automated software toolkit.

9:50 AM  
First Principles Thermodynamics of Fe-Cr-Mn Carbides in High-Mn Steels: Lekshmi Sreekala1; Tilmann Hickel1; Jörg Neugebauer1; 1Max-Planck-Institute For Iron Research
    Alloying high-Mn steels with several elements provides attractive candidate materials in high performance engineering applications because of their high strength and toughness. Adding alloying elements such as Cr makes the material corrosion resistant, which is relevant for applications in harsh environments. Recent experiments reported that alloying with Cr substantially increases the number of carbides, like M3C and M23C6 where M being a mixture of Fe, Cr and Mn. In the present work, we therefore use density functional theory to determine the thermodynamic driving force for the formation of carbides as a function of the chemical composition of the alloy. These investigations are performed at finite temperatures considering the vibrational, the electronic and the magnetic contributions to the free energy of formation. We analyse the critical role of Cr by determining the partitioning of Cr and Mn into the carbides.

10:10 AM  
Interplay between Chemical Interactions and Constituent Strain Energy during the Early Stages of Precipitations: Kang Wang1; Du Cheng1; Bi-Cheng Zhou1; 1University of Virginia
    Favored alloy configurations in solid solutions at the atomic scale dictate the ordering / clustering tendencies and affect the structures, stabilities and morphologies of precipitates. In the past, the theoretical investigations of the favored alloy configurations in Mg alloys primarily centered on the short-ranged chemical interactions. However, it is known that long-ranged strain energy caused by size mismatch between constituent species, especially its anisotropy, plays an important role in the early stages of precipitation. In the current work, the energies due to chemical interactions and constituent strain are separated by the first-principles mixed-space cluster expansion approach, and their roles on the short-range ordering / clustering and precipitation in binary Mg alloys are examined comprehensively with a focus on the formation of Guinier-Preston (G.P.) zones. And the metastable phase diagrams with potential G.P. zones are constructed with both chemical and strain energy contributions.