Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session V41: Metals: StructuralLive
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Sponsoring Units: DCMP Chair: Jason Haraldsen, University of North Florida |
Thursday, March 18, 2021 3:00PM - 3:12PM Live |
V41.00001: Pressure effect on the diffusion of carbon at the 85.91o <100> symmetric tilt grain boundary of α-iron Md Mijanur Rahman, Fedwa El-Mellouhi, Othmane Bouhali, Charlotte S. Becquart, Normand Mousseau The diffusion mechanisms (DMs) of C atom around grain boundaries (GBs) in α-iron have long been an area of interest for researchers due to its impact on various mechanical properties for steel such as corrosion resistance and embrittlement. Over the years, these mechanisms have been studied at ambient pressure. However, to date effect of pressure on the DMs of C in GBs of iron has received much less attention and relatively little information is available. In this study, using the kinetic activation-relaxation technique an off-lattice KMC algorithm with on-the-fly catalog building that allows obtaining diffusion properties over large time scales taking full account of chemical and elastic effects coupled with an EAM potential, we investigate the pressure effect on the diffusion properties of C in 85.91o <100> symmetric tilt GB of α-iron within a range of -1.2GPa to 1.2GPa at a temperature of 600K. We find that, at zero pressure, the C atom segregates to the GB region and traps in energy states lower than found in the crystal. This segregation increases with increasing pressure. Moreover, the effective barriers of C diffusion at the GB increase with increasing pressure. This suggests that at higher pressure C will be pinned by the compression of the boundary, slowing diffusion. |
Thursday, March 18, 2021 3:12PM - 3:24PM Live |
V41.00002: Bayesian optimization of high entropy alloy properties Franco Moitzi, Lorenz Romaner, Andrei Ruban, Oleg Peil High entropy alloys, or better termed as multi-principal element solid solution alloys (MPEA), represent a class of |
Thursday, March 18, 2021 3:24PM - 3:36PM Live |
V41.00003: Development of Reference-free (RF) MEAM Interatomic Potentials for Transition Metal-rich Carbides Tyler McGilvry-James, Andrew Ian Duff, Bikash Timalsina, Alin Niraula, Muztoba Rabbani, Nirmal Baishnab, Puja Adhikari, Saro San, Wai-Yim Ching, Ridwan Sakidja Reference-free (RF) MEAMfit code has been used to develop Reference-free Modified Embedded Atom Method (RF-MEAM) interatomic potentials. These potentials were optimized for a variety of transition metal rich carbides with a focus in modeling the thermodynamic stability and thermo-mechanical properties of the M23C6 and MC – type phases. The stability of these phases is critical to the high-temperature creep resistance of polycrystalline Ni-based Superalloys. The MEAM interatomic potentials utilized datasets of energy, force, and stress tensor information from the DFT calculations. |
Thursday, March 18, 2021 3:36PM - 3:48PM Live |
V41.00004: Influence of Mn on nanoscale precipitate formation in Al-Cu-Mn alloys ZHAOHAN ZHANG, Samarendra Roy, Shibayan Roy, Rohan Mishra Aluminum alloys having high strength and low density are promising for use in transportation industry. Recent studies have shown that the addition of Mn to Al-Cu alloys stabilizes metastable precipitates by segregating to alloy-precipitate interfaces, and allows the alloys to retain strength at higher temperatures. In this work, we fabricated Al-Cu-Mn alloys with varying Mn concentration (0.3-1% wt.) and investigated the formation of nanoscale precipitates viz. θ' and T-phases. While at high Mn content (1% wt.), we observed an overwhelming majority of T-phase precipitates and overall higher hardness under isothermal aging. With decreasing Mn content, the precipitation of T-phase is suppressed and a high density of θ' precipitates are observed. First-principles density-functional-theory calculations show that the interface energy of θ' with Al matrix is lower compared to that of the T-phase, which is one of the key factors that govern nanostructure evolution with varying Mn addition. We will also investigate other factors including Mn segregation and elastic-strain energy on alloy-precipitate interfaces. |
Thursday, March 18, 2021 3:48PM - 4:00PM Live |
V41.00005: Investigation of electric current-assisted fabrication parameters for nanocarbon-Al composites with improved electrical conductivity and tensile strength Madeline Morales, Xiaoxiao Ge, Christopher J Klingshirn, Lourdes Salamanca-Riba Electric current-assisted processing of a class of materials, called “covetics,” presents a scalable method of production for nanocarbon-Al composites by applying a direct current to a molten mixure of Al-1350 and activated carbon precursor. Increased tensile strength and electrical conductivity have been measured in Al covetics; however, there is limited understanding of the current-assisted process parameters and variation in structure and properties among trials. Within the metal matrix the activated carbon is converted to sp2 graphitic carbon with increased crystallite size of the graphitic carbon, as measured by the Tuinstra-Koenig relation for Raman spectra. Electrical conductivity is enhanced in areas that show increased crystallite size of the graphitic carbon. Applied current during fabrication has been varied to understand the effect of current density on carbon crystallization rate. Local electromechanical behavior is measured by nanoindentation and AFM to gain insight into the structure-property relationship at the nanoscale, which can be used to further inform optimization of the current-assisted process. |
Thursday, March 18, 2021 4:00PM - 4:12PM Live |
V41.00006: Vacancy-mediated Phase Selection in High-Entropy Alloys Prashant Singh, Shalabh Gupta, Matthew J Kramer, Duane D. Johnson We highlight the importance of vacancy-mediated stability in refractory high-entropy |
Thursday, March 18, 2021 4:12PM - 4:24PM Live |
V41.00007: Surface-stress induced embrittlement of metals Anirudh Udupa, Tatsuya Sugihara, Koushik Viswanathan, Srinivasan Chandrasekar Adsorbed films often influence mechanical behavior of surfaces, leading to well-known mechanochemical phenomena such as liquid metal embrittlement and environment-assisted cracking. Here, we demonstrate a novel mechanochemical phenomenon wherein adsorbed long-chain organic monolayers disrupt large-strain plastic deformation in metals. Using high-speed in situ imaging and post-facto analysis, we show that the monolayers induce a ductile-to-brittle transition. Sinuous flow, characteristic of ductile metals, gives way to quasi-periodic fracture, typical of brittle materials, with 85% reduction in deformation forces. By independently varying surface energy and molecule chain length via molecular self-assembly, we show that this “embrittlement” is driven by adsorbate-induced surface stress, as against surface energy reduction. Our observations, backed by modeling and molecular simulations, could provide a basis for explaining diverse mechanochemical phenomena in solids. Additionally, the results have implications for manufacturing processes such as machining and comminution, and wear. |
Thursday, March 18, 2021 4:24PM - 4:36PM Live |
V41.00008: Stabilities and mechanical properties of novel Mg-based light metal compositionally complex alloys Wernfried Mayr-Schmölzer, Johannes Kirschner, Clemens Simson, Christoph Eisenmenger-Sittner, Johannes Bernardi, Gregor Vonbun-Feldbauer Compositionally Complex Alloys (CCAs) consist of four or more elements alloyed in approximately equal fractions and often crystallize in a simple crystal lattice. In many cases, their mechanical properties like structural stability or ductility exceed that of common modern alloys. Usually they contain heavy d-Orbital metals, but investigations into low density light metal CCAs have been rare up to now due to the complex binding modes of their constituents. |
Thursday, March 18, 2021 4:36PM - 4:48PM Live |
V41.00009: Effect of full potential treatment of semi-core states on shear elastic constants Fuyang Tian, Yang Wang In ab initio electronic structure calculations, the core-states are usually treated as bound state and are calculated by solving the Kohn-Sham equation with spherical potential approximation and an appropriate boundary condition. While in most cases such treament of the core states works well, under certain circumtances, e.g. materials under high pressure or with strong mechanical anisotropy, the non-spherical crystal field has significant effects on the semi-core electronic states, and consequently on the physical and chemical properties of the materials. In this presentation, we show a full-potential Green function approach to the treatment of the semi-core states which does not require the spherical potential approximation. We discuss the effect of semi-core states on the equation of state and elastic constants for bcc, fcc and hcp bulk metallic materials. Our calculations show that the full potential treatment of semi-core states causes the equilibrium lattice constant to decrease and the bulk moduli to increase. We find that the full-potential treatments improve the elastic constants cij, especially shear elastic constant c44 results. |
Thursday, March 18, 2021 4:48PM - 5:00PM Live |
V41.00010: Thermomechanical conversion in metals: dislocation plasticity model evaluation of the Taylor-Quinney coefficient Charles Lieou, Curt A Bronkhorst Using a partitioned-energy thermodynamic framework which assigns energy to that of atomic configurational stored energy of cold work and kinetic-vibrational, we derive an important constraint on the Taylor-Quinney coefficient, which quantifies the fraction of plastic work that is converted into heat during plastic deformation. Associated with the two energy contributions are two separate temperatures -- the ordinary temperature for the thermal energy and the effective temperature for the configurational energy. We show that the Taylor-Quinney coefficient is a function of the thermodynamically defined effective temperature that measures the atomic configurational disorder in the material. Finite-element analysis of recently published experiments on the aluminum alloy 6016-T4, using the thermodynamic dislocation theory (TDT), shows good agreement between theory and experiment for both stress-strain behavior and temporal evolution of the temperature. The simulations include both conductive and convective thermal energy loss during the experiments. Computed values of the differential Taylor-Quinney coefficient are also presented and suggest a value which differs between materials and increases with increasing strain. |
Thursday, March 18, 2021 5:00PM - 5:12PM Live |
V41.00011: Hybrid Cuckoo Search for Accelerating Modeling and Design of High-Entropy Alloys Duane D. Johnson, Prashant Singh, Ganesh Balasubramanian High-entropy alloys in competing crystal structures have a huge design spaces for unique chemical and mechanical properties. To enable computational design, we use a metaheuristic Hybrid Cuckoo Search (CS) to construct models on-the-fly having targeted atomic site and pair probabilities on arbitrary crystal lattices, configurations represented by Super-Cell Random APproximates (SCRAPs). Our Hybrid CS permits ultrafast global solutions for large, discrete combinatorial optimization that scale linearly in system size and in number of parallel processors (strong scaling). For example, a small system given by 4-element, 128-site SCRAP is found in seconds -- a reduction of 13,000+ over current strategies. With model-generation eliminated as a bottleneck, computational alloy design can be performed that was formerly impossible or impractical. We showcase the method for real alloys with varying atomic short-range order. |
Thursday, March 18, 2021 5:12PM - 5:24PM Live |
V41.00012: Revealing nanoscale local chemical environments governing diffusion within binary concentrated alloys through machine learning S. Mohadeseh Taheri-Mousavi, S. Sina Moeini-Ardakani, Ryan W. Penny, Ju Li, A. John Hart Bulk diffusion in binary and multi-component alloys is governed by correlated nanoscale mechanisms that strongly depend on the configuration of alloying elements near vacancies. Here, we present a numerical framework wherein a deep-learning algorithm supervised by atomistic-scale simulations is used to explore the immense configurational breadth of alloys near vacancies. We apply this framework to predict associated energies for the exchange of atomic sites with vacancies. For a model Ni1-xAlx system, our approach has less than 1 meV error in prediction of the formation energy, while being trained by data representing only 10% of the total compositional space. We reveal that in a Ni matrix, exchanging sites of vacancies with Al atoms has a higher average energy barrier and formation energy than for Ni atoms, and this governs the mobility and interdiffusion coefficient of Al in Ni. Moreover, the propensity of Al to form short-range-order near vacancies correlates with the generalized stacking fault energy of configurations with mobile Ni atoms. Future applications of this framework include studying the diffusivity of multi-component alloys as well as crystals under different mechanical and thermal boundary conditions. |
Thursday, March 18, 2021 5:24PM - 5:36PM On Demand |
V41.00013: Screening corrosion-resistant binary magnesium alloys through high-throughput computations Yaowei Wang, Tian Xie, Hong Zhu Magnesium (Mg) alloys have shown great potential as both structural and biomedical materials due to their high strength-to-weight ratio and good biocompatibility. However, poor corrosion resistance limits their further application, while alloying is believed to be one of the most effective strategies to develop corrosion-resistant Mg alloys. Recently, high-throughput computational method has become a useful tool to screen promising materials for various applications. In this work, we first collected 27919 (including repeated) Mg intermetallics structures from online databases, from which 332 stable candidates were selected. Then, the equilibrium potential based on Nernst equation were calculated and 50 Mg intermetallics with smallest equilibrium potential difference from that of Mg matrix and hence the lowest thermodynamic driving force of galvanic corrosion were reserved. From the idea of small cathodic exchange current density and thermodynamic driving force of galvanic corrosion, several intermetallics were selected to be the promising phases for corrosion-resistant binary alloys. Our work provides a high-throughput screening strategy for corrosion-resistant alloy design, which can also be extended to screen ternary intermetallics or other alloy systems. |
Thursday, March 18, 2021 5:36PM - 5:48PM On Demand |
V41.00014: A data-driven approach to study the order-disorder transition in high entropy alloys Xianglin Liu, Jiaxin Zhang, Junqi Yin, Siyu Bi, Markus Eisenbach, Yang Wang We introduce a data-driven approach to construct the effective Hamiltonian from first principles data, and apply it to study the thermodynamics of HEAs through canonical Monte Carlo simulation. This method uses atomic pair interactions as features and systematically improve the representativeness of the dataset using samples from Monte Carlo simulation. This method produces highly accurate effective Hamiltonians that give less than 0.1 mRy test error for all the three refractory HEAs: MoNbTaW, MoNbTaVW, and MoNbTaTiW. From the Monte Carlo results, we identified two order-disorder transition temperatures, each due to different chemical interactions. By comparing with experimental results, we propose that by tuning the chemical composition, the order and disorder phases can be controlled, which further affects the strength and ductility of HEAs. |
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