Computational Thermodynamics and Kinetics: Microstructural Evolution and Phase Stability I
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
Monday 8:00 AM
February 24, 2020
Room: 33C
Location: San Diego Convention Ctr
Session Chair: Alexander Chadwick, Northwestern University; Christopher Weinberger, Colorado State University
8:00 AM Invited
The Evolution of Bicontinuous Structures by Interfacial and Bulk Diffusion: W. Beck Andrews1; Kate Elder2; Katsuyo Thornton1; Peter Voorhees2; 1University of Michigan; 2Northwestern University
Bicontinuous two-phase mixtures are found in systems ranging from block copolymers to phase separated alloys and nanoporous metals. We employ the prototypical bicontinuous structure found following spinodal decomposition to probe the morphology and evolution of bicontinuous two-phase mixtures that are coarsening by either interfacial or bulk diffusion using two-point statistics, the interfacial topology, and interfacial shape distribution. Two different phase field models for interface diffusion are employed, and the differences in results between these two approaches will be discussed. Even though interfacial and bulk diffusion dynamics are completely different, we find that the interfacial morphologies are very similar for systems with 32% and 36% volume fractions. Structures with 30% volume fraction break into independent particles, while those with 32% volume fraction do not, emphasizing the impact a small change in volume fraction can have on the evolution process.
8:20 AM
Phase Stability, Chemo-mechanics and Microstructure Space in TiAlZrN Ultra-hard Nanocoatings: Vahid Attari1; Raymundo Arroyave1; 1Texas A&M University
TiAlZrN cubic alloys within the 25–70% Al composition range have high age-hardening capabilities due to metastable phase transition pathways at high temperatures. They are thus ideal candidates for ultra-hard nano-coating materials. There is growing evidence that this effect is associated with the elasto-chemical field-induced phase separation into compositionally-segregated nanocrystalline nitride phases. Our simulations indicate that elastic interactions between nitride nano-domains greatly affect not only the morphology of the microstructure but also the local chemical phase equilibria. In Al-rich regions of the composition space we further observe the onset of the transformation of AlN-rich phases into their equilibrium wurtzite crystal structure. This work points to a wide palette of microstructures potentially accessible to these nitride systems and their tailoring is likely to result in significant improvements in the performance of transition metal nitride-based coating materials.
8:40 AM
Multiscale Modeling of Mass Transport in Transition Metal Carbides: Rofiques Salehin1; Xiaochuan Tang1; Gregory Thompson2; Christopher Weinberger1; 1Colorado State University; 2University of Alabama
Mass transport in the transition metal carbides can is complicated because these materials are strongly nonstoichiometric and exhibit both metallic and covalent bonding. Furthermore, mass transport is a critical property in these materials as they are used as structural materials at extreme temperatures and regularly subjected to creep loading. To provide an understanding of mass transport and creep in these materials we combine density functional theory, cluster expansion methods, Monte Carlo and kinetic Monte Carlo to explore how the carbon and metal atoms diffuse. Specifically, we compute the formation and migration energies of a wide range of defect complexes in these materials from DFT and extend them to larger scales with cluster expansion and Monte Carlo methods. Our results show that in the group IVB carbides the main mechanism is through a coordinated vacancy cluster migration method while in the VB carbides the vacancy migration is typically uncoordinated.
9:00 AM Invited
Microstructure Formation from Atomistic Viewpoint: Yasushi Shibuta1; 1The University of Tokyo
Kinetics in microstructure formation is investigated by large-scale and long-time molecular dynamics (MD) simulations of contentious processes of nucleation, solidification and grain growth in a submicrometer-scale system. The grain growth exponent obtained from the MD simulation deviates from the ideal value since anisotropic effects in the grain boundary properties are inherently included in MD simulations. The dominant factor for the deviation from the ideal grain growth is closely discussed. Moreover, our new achievement bridging the gap between atomistic and microstructural scale simulations is introduced, in which molecular dynamics-generated atomic configurations of microstructure are converted into interfacial profiles of the phase-field model. [1] Okita et al., Acta Mater 153 (2018) 103. [2] Miyoshi et al., Comp. Mater. Sci. 152 (2018) 118.
9:30 AM Break
9:50 AM Invited
Phase Field Modeling and Simulation Study of Multiferroic Magnetoelectric Composite Materials: Yongmei Jin1; Liwei Geng1; Yu Wang1; 1Michigan Technological University
Multiferroic magnetoelectric composites composed of magnetostrictive and piezoelectric materials offer unique properties and functionalities that cannot be obtained in individual constituent materials, thus enabling development of new devices and technology. Phase field model is developed to perform computational study of strain-mediated domain-level magnetization-polarization coupling mechanisms in the composites. Phase morphology, grain microstructure, internal stress distribution, and magnetization and polarization domain processes are simulated. The interplays among magnetocrystalline anisotropy, stress-induced anisotropy, and internal residual bias stress are studied in quantitative details. Various magnetostrictive constituents (Metglas, Terfenol-D, ferrite) are considered for their distinct properties: amorphous Metglas with very weak material magnetic anisotropy and small magnetostriction, polycrystalline Terfenol-D with strong magnetocrystalline anisotropy and large magnetostriction, and ferrite in between. Examples of magnetoelectric coefficient and voltage-tunable magnetic susceptibility are presented for sensor and tunable inductor applications.
10:20 AM
Probing Solid-solid Interfacial Reactions in All-solid-state Batteries: Hanmei Tang1; Zhi Deng1; Abhik Banerjee1; Erik Wu1; Han Nguyen1; Zhuoying Zhu1; Shirley Meng1; Shyue Ping Ong1; 1University of California, San Diego
We have developed a hierarchy of DFT-based approaches to understand and design electrode/buffer/SE interfaces in all-solid-state batteries. With relatively efficient thermodynamics approximations, we reveal that S-O exchange reactions between oxides and thiophosphates resulting in the formation of phosphates are responsible for large reaction driving force between common NaMO2 cathodes and Na3PS4 electrolyte. Such reactions, with their associated large volume changes, can be mitigated by careful selection of the cathode/SE combination, or by applying coatings. We further demonstrate that explicit modelling of the electrode/SE interface via AIMD simulations yield different and more realistic predictions of interfacial reactions. For example, AIMD predicts that formation of SO42– and is kinetically favored over the formation of PO43– at the NaCoO2/Na3PS4 interface. These observations have been validated experimentally. We have also extended such studies to the LiNi0.85Co0.1Al0.05O2/Li6PS5Cl interface, with and without buffer layers, and the predicted interfacial reactions are in good agreement with experimental characterizations.
10:40 AM
Phase-field Model of Kirkendall Porosity Formation During Ti/Ni Interdiffusion to Form NiTi Microwires: Alexander Chadwick1; David Dunand1; Peter Voorhees1; 1Northwestern University
Recent experimental studies of the formation of NiTi microwires through gas-phase Ti-deposition on Ni wires and homogenization revealed that Ti/Ni interdiffusion (from Ni+Ti to NiTi) is accompanied by a pronounced Kirkendall effect that generates porosity near phase boundaries during Ni/Ti interdiffusion. While phase-field simulations have demonstrated quantitative agreement against experiments for phase transformations in multicomponent alloys, they typically have not included either vacancy transport or porosity formation. We therefore present a grand potential phase-field model of the Ti/Ni interdiffusion process. The vacancy transport and reaction kinetics of the model are verified against sharp-interface descriptions derived through irreversible thermodynamics. We apply the model to the binary NiTi system and examine how the transport of vacancies and atoms, interfacial reaction kinetics, and the geometry of the microwire all affect the predicted porosity in the final microstructure. The simulation results are compared to experiments for validation.
11:00 AM Invited
Localized Phase Equilibria and Dynamic Phase Transformations at Extended Defects – a New Alloy Design Strategy for Unprecedented Properties: Longsheng Feng1; Yipeng Gao2; Dong Wang3; Yufeng Zheng1; Michael Mills1; Hamish Fraser1; Yunzhi Wang1; 1The Ohio State University; 2Idaho National Laboratory; 3Xi'an Jiao Tong University
Extended defects in crystalline solids such as dislocations, grain boundaries, stacking faults, and deformation twins may alter phase equilibria and change phase transformation behavior. The recent discovery of dynamic phase transformations at extended defects has attracted a lot of attention. They have been shown to have the ability to (a) significantly improve the high-temperature creep performance of Ni-base superalloys and, (b) make metastable beta Ti-alloys ultralow modulus and non-hysteretic, linear superelastic. In this presentation, we analyze fundamental characteristics of such localized phase equilibria and dynamic phase transformations at stacking faults and deformation twin boundaries and their impact on the mechanical behavior of these alloys using a combined CALPHAD, phase transition graph (PTG) and phase field approaches. This study may shed light on employing novel processing routes to stabilize nano precipitate structures, thereby providing new strengthening and deformation mechanisms for these alloys. The work is supported by NSF under DMREF programs.