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Moravcik I, Zelený M, Dlouhy A, Hadraba H, Moravcikova-Gouvea L, Papež P, Fikar O, Dlouhy I, Raabe D, Li Z. Impact of interstitial elements on the stacking fault energy of an equiatomic CoCrNi medium entropy alloy: theory and experiments. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2022; 23:376-392. [PMID: 36081838 PMCID: PMC9448438 DOI: 10.1080/14686996.2022.2080512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 04/25/2022] [Accepted: 05/17/2022] [Indexed: 06/15/2023]
Abstract
We investigated the effects of interstitial N and C on the stacking fault energy (SFE) of an equiatomic CoCrNi medium entropy alloy. Results of computer modeling were compared to tensile deformation and electron microscopy data. Both N and C in solid solution increase the SFE of the face-centered cubic (FCC) alloy matrix at room temperature, with the former having a more significant effect by 240% for 0.5 at % N. Total energy calculations based on density functional theory (DFT) as well as thermodynamic modeling of the Gibbs free energy with the CALPHAD (CALculation of PHAse Diagrams) method reveal a stabilizing effect of N and C interstitials on the FCC lattice with respect to the hexagonal close-packed (HCP) CoCrNi-X (X: N, C) lattice. Scanning transmission electron microscopy (STEM) measurements of the width of dissociated ½<110> dislocations suggest that the SFE of CoCrNi increases from 22 to 42-44 mJ·m-2 after doping the alloy with 0.5 at. % interstitial N. The higher SFE reduces the nucleation rates of twins, leading to an increase in the critical stress required to trigger deformation twinning, an effect which can be used to design load-dependent strain hardening response.
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Affiliation(s)
- Igor Moravcik
- Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, NETME Centre, Brno, Czech Republic
- Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
| | - Martin Zelený
- Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, NETME Centre, Brno, Czech Republic
| | - Antonin Dlouhy
- Institute of Physics of Materials of the Czech Academy of Sciences, Brno, Czech Republic
| | - Hynek Hadraba
- Institute of Physics of Materials of the Czech Academy of Sciences, Brno, Czech Republic
| | - Larissa Moravcikova-Gouvea
- Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, NETME Centre, Brno, Czech Republic
| | - Pavel Papež
- Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, NETME Centre, Brno, Czech Republic
| | - Ondřej Fikar
- Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, NETME Centre, Brno, Czech Republic
- Institute of Physics of Materials of the Czech Academy of Sciences, Brno, Czech Republic
| | - Ivo Dlouhy
- Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, NETME Centre, Brno, Czech Republic
- Institute of Physics of Materials of the Czech Academy of Sciences, Brno, Czech Republic
| | - Dierk Raabe
- Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
| | - Zhiming Li
- Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
- School of Materials Science and Engineering, Central South University, Changsha, China
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Samolyuk GD, Osetsky YN, Stocks GM, Morris JR. Role of Static Displacements in Stabilizing Body Centered Cubic High Entropy Alloys. PHYSICAL REVIEW LETTERS 2021; 126:025501. [PMID: 33512181 DOI: 10.1103/physrevlett.126.025501] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 11/12/2020] [Indexed: 06/12/2023]
Abstract
The configurational entropy of high entropy alloys (HEAs) plays little role in the stabilization of one particular crystal structure over another. We show that disorder-induced atomic displacements help stabilize body centered cubic (bcc) structure HEAs with average valences <4.7. These disorder-induced atomic displacements mimic the temperature-induced vibrations that stabilize the bcc structure of group IV elemental metals at high temperatures. The static displacements are significantly larger than for face centered cubic HEAs, approaching values associated with the Lindemann criterion for melting. Chemical disorder in high entropy alloys have a previously unidentified, nonentropic energy contribution that stabilizes a particular crystalline ground state.
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Affiliation(s)
- G D Samolyuk
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y N Osetsky
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G M Stocks
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J R Morris
- Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
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A Review of Multi-Scale Computational Modeling Tools for Predicting Structures and Properties of Multi-Principal Element Alloys. METALS 2019. [DOI: 10.3390/met9020254] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Multi-principal element (MPE) alloys can be designed to have outstanding properties for a variety of applications. However, because of the compositional and phase complexity of these alloys, the experimental efforts in this area have often utilized trial and error tests. Consequently, computational modeling and simulations have emerged as power tools to accelerate the study and design of MPE alloys while decreasing the experimental costs. In this article, various computational modeling tools (such as density functional theory calculations and atomistic simulations) used to study the nano/microstructures and properties (such as mechanical and magnetic properties) of MPE alloys are reviewed. The advantages and limitations of these computational tools are also discussed. This study aims to assist the researchers to identify the capabilities of the state-of-the-art computational modeling and simulations for MPE alloy research.
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Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films. MATERIALS 2019; 12:ma12040587. [PMID: 30781407 PMCID: PMC6416794 DOI: 10.3390/ma12040587] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/08/2019] [Accepted: 02/13/2019] [Indexed: 12/18/2022]
Abstract
In this study, we show that the phase formation of HfNbTiVZr high-entropy thin films is strongly influenced by the substrate temperature. Films deposited at room temperature exhibit an amorphous microstructure and are 6.5 GPa hard. With increasing substrate temperature (room temperature to 275 °C), a transition from an amorphous to a single-phased body-centred cubic (bcc) solid solution occurs, resulting in a hardness increase to 7.9 GPa. A higher deposition temperature (450 °C) leads to the formation of C14 or C15 Laves phase precipitates in the bcc matrix and a further enhancement of mechanical properties with a peak hardness value of 9.2 GPa. These results also show that thin films follow different phase formation pathways compared to HfNbTiVZr bulk alloys.
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Li X, Irving DL, Vitos L. First-principles investigation of the micromechanical properties of fcc-hcp polymorphic high-entropy alloys. Sci Rep 2018; 8:11196. [PMID: 30046064 PMCID: PMC6060180 DOI: 10.1038/s41598-018-29588-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/09/2018] [Indexed: 11/25/2022] Open
Abstract
High-entropy alloys offer a promising alternative in several high-technology applications concerning functional, safety and health aspects. Many of these new alloys compete with traditional structural materials in terms of mechanical characteristics. Understanding and controlling their properties are of the outmost importance in order to find the best single- or multiphase solutions for specific uses. Here, we employ first-principles alloy theory to address the micro-mechanical properties of five polymorphic high-entropy alloys in their face-centered cubic (fcc) and hexagonal close-packed (hcp) phases. Using the calculated elastic parameters, we analyze the mechanical stability, elastic anisotropy, and reveal a strong correlation between the polycrystalline moduli and the average valence electron concentration. We investigate the ideal shear strength of two selected alloys under shear loading and show that the hcp phase possesses more than two times larger intrinsic strength than that of the fcc phase. The derived half-width of the dislocation core predicts a smaller Peierls barrier in the fcc phase confirming its increased ductility compared to the hcp one. The present theoretical findings explain a series of important observations made on dual-phase alloys and provide an atomic-level knowledge for an intelligent design of further high-entropy materials.
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Affiliation(s)
- Xiaoqing Li
- Department of Materials Science and Engineering, KTH-Royal Institute of Technology, 10044, Stockholm, Sweden.
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, 27695, USA.
- Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, Budapest, H-1525, Hungary.
| | - Douglas L Irving
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, 27695, USA
| | - Levente Vitos
- Department of Materials Science and Engineering, KTH-Royal Institute of Technology, 10044, Stockholm, Sweden
- Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, Budapest, H-1525, Hungary
- Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, SE-75120, Uppsala, Sweden
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Waseem OA, Ryu HJ. Powder Metallurgy Processing of a W xTaTiVCr High-Entropy Alloy and Its Derivative Alloys for Fusion Material Applications. Sci Rep 2017; 7:1926. [PMID: 28512337 PMCID: PMC5434025 DOI: 10.1038/s41598-017-02168-3] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 04/07/2017] [Indexed: 11/09/2022] Open
Abstract
The WxTaTiVCr high-entropy alloy with 32at.% of tungsten (W) and its derivative alloys with 42 to 90at.% of W with in-situ TiC were prepared via the mixing of elemental W, Ta, Ti, V and Cr powders followed by spark plasma sintering for the development of reduced-activation alloys for fusion plasma-facing materials. Characterization of the sintered samples revealed a BCC lattice and a multi-phase structure. The selected-area diffraction patterns confirmed the formation of TiC in the high-entropy alloy and its derivative alloys. It revealed the development of C15 (cubic) Laves phases as well in alloys with 71 to 90at.% W. A mechanical examination of the samples revealed a more than twofold improvement in the hardness and strength due to solid-solution strengthening and dispersion strengthening. This study explored the potential of powder metallurgy processing for the fabrication of a high-entropy alloy and other derived compositions with enhanced hardness and strength.
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Affiliation(s)
- Owais Ahmed Waseem
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehakro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Ho Jin Ryu
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehakro, Yuseong-gu, Daejeon, 34141, Republic of Korea.
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Lattice Distortions in the FeCoNiCrMn High Entropy Alloy Studied by Theory and Experiment. ENTROPY 2016. [DOI: 10.3390/e18090321] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Li X, Schönecker S, Li R, Li X, Wang Y, Zhao J, Johansson B, Vitos L. Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:295501. [PMID: 27255428 DOI: 10.1088/0953-8984/28/29/295501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W1-x-y Re x Os y (0 ⩽ x, y ⩽ 6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11, the other elastic parameters including C 12, C 44, Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W1-y Os y than in W1-x Re x . A strong correlation between C' and the fcc-bcc structural energy difference for W1-x-y Re x Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.
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Affiliation(s)
- Xiaojie Li
- Key Laboratory of Materials Modification by Laser, Electron, and Ion Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, People's Republic of China. Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm SE-10044, Sweden
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