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Study on Transformation Mechanism and Kinetics of α’ Martensite in TC4 Alloy Isothermal Aging Process. CRYSTALS 2020. [DOI: 10.3390/cryst10030229] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The law of microstructure evolution and transformation mechanism of the α′ martensite decomposition during 400–600 °C were studied by the isothermal dilatometry. The transformation process of α′ martensite was quantitatively characterized based on Johnson–Mehl–Avrami (JMA) model, and the microstructure evolution under different aging processes was observed and compared on Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results showed that α′ → α + β is the elemental diffusion transformation, the position and shape of the precipitate gradually change with the holding time and temperature. The decomposition rate of α′ martensite was positively correlated with the aging temperature. The whole transformation process was divided into two stages based on the value of the Avrami exponent n, and the corresponding average values of the transformation activation energies Q are 46.1 kJ/mol and 116.8 kJ/mol, respectively. The calculated model had good agreement with the experimental data, and the transformation curve of α′ martensite with time and temperature during the isothermal aging at 400–600 °C was drawn.
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Abstract
In order to understand the non-isothermal transformation behavior of Ti-6Al-4V titanium alloy in the continuous heating stage of solution treatment, thermal dilatometry tests with heating rates of 0.1~0.8 °C/s were designed. The conversion between the expansion amount and the transformed volume fraction was realized by the lever principle, and the transformation characteristics of α + β → β were quantified based on the Kissinger-Akahira-Sunose (KAS) theory and the modified Johnson–Mehl–Avrami (JMA) model. The results show that the phase transformation kinetics curves present typical “S” patterns, and the element diffusion transformation controls the nucleation and growth of new grains during the transformation of α + β → β. The phase transformation interval gradually moves to high temperature regions with the increase of heating rates, and the phase transformation activation energy is 445.5 kJ·mol−1. The phase transformation process is divided into three stages according to the relationship between the Avrami exponent n and the transformed volume fraction fT. These three stages correspond to different stages of grain nucleation or growth.
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DFT Calculations of the Structural, Mechanical, and Electronic Properties of TiV Alloy Under High Pressure. Symmetry (Basel) 2019. [DOI: 10.3390/sym11080972] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A calculation program based on the density functional theory (DFT) is applied to study the structural, mechanical, and electronic properties of TiV alloys with symmetric structure under high pressure. We calculate the dimensionless ratio, elastic constants, shear modulus, Young’s modulus, bulk modulus, ductile-brittle transition, material anisotropy, and Poisson’s ratio as functions of applied pressure. Results suggest that the critical pressure of structural phase transition is 42.05 GPa for the TiV alloy, and structural phase transition occurs when the applied pressure exceeds 42.05 GPa. High pressure can improve resistance to volume change, as well as the ductility and atomic bonding, but the strongest resistances to elastic and shear deformation occur at P = 5 GPa for TiV alloy. Furthermore, the results of the density of states (DOS) indicate that the TiV alloy presents metallicity. High pressure disrupts the structural stability of the TiV alloy with symmetry, thereby inducing structural phase transition.
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O'Bannon EF, Jenei Z, Cynn H, Lipp MJ, Jeffries JR. Contributed Review: Culet diameter and the achievable pressure of a diamond anvil cell: Implications for the upper pressure limit of a diamond anvil cell. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:111501. [PMID: 30501343 DOI: 10.1063/1.5049720] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 10/14/2018] [Indexed: 06/09/2023]
Abstract
Recently, static pressures of more than 1.0 TPa have been reported, which raises the question: what is the maximum static pressure that can be achieved using diamond anvil cell techniques? Here we compile culet diameters, bevel diameters, bevel angles, and reported pressures from the literature. We fit these data and find an expression that describes the maximum pressure as a function of the culet diameter. An extrapolation of our fit reveals that a culet diameter of 1 μm should achieve a pressure of ∼1.8 TPa. Additionally, for pressure generation of ∼400 GPa with a single beveled diamond anvil, the most commonly reported parameters are a culet diameter of ∼20 μm, a bevel angle of 8.5°, and a bevel diameter to culet diameter ratio between 14 and 18. Our analysis shows that routinely generating pressures more than ∼300 GPa likely requires diamond anvil geometries that are fundamentally different from a beveled or double beveled anvil (e.g., toroidal or double stage anvils) and culet diameters that are ≤20 μm.
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Affiliation(s)
- Earl F O'Bannon
- Physical and Life Sciences, Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
| | - Zsolt Jenei
- Physical and Life Sciences, Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
| | - Hyunchae Cynn
- Physical and Life Sciences, Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
| | - Magnus J Lipp
- Physical and Life Sciences, Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
| | - Jason R Jeffries
- Physical and Life Sciences, Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
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Lindwall G, Wang P, Kattner UR, Campbell CE. The Effect of Oxygen on Phase Equilibria in the Ti-V System: Impacts on the AM Processing of Ti Alloys. JOM (WARRENDALE, PA. : 1989) 2018; 70:1692-1705. [PMID: 30956517 PMCID: PMC6417434 DOI: 10.1007/s11837-018-3008-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 06/21/2018] [Indexed: 06/09/2023]
Abstract
Oxygen is always a constituent in "real" titanium alloys including titanium alloy powders used for powder-based additive manufacturing (AM). In addition, oxygen uptake during powder handling and printing is hard to control and, hence, it is important to understand and predict how oxygen is affecting the microstructure. Therefore, oxygen is included in the evaluation of the thermodynamic properties of the titanium-vanadium system employing the CALculation of PHAse Diagrams method and a complete model of the O-Ti-V system is presented. The β-transus temperature is calculated to increase with increasing oxygen content whereas the extension of the α-Ti phase field into the binary is calculated to decrease, which explains the low vanadium solubilities measured in some experimental works. In addition, the critical temperature of the metastable miscibility gap of the β-phase is calculated to increase to above room temperature when oxygen is added. The effects of oxygen additions on phase fractions, martensite and ω formation temperatures are discussed, along with the impacts these changes may have on AM of titanium alloys.
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Affiliation(s)
- Greta Lindwall
- Materials Science and Engineering Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8555, Gaithersburg, MD 20899-8555 USA
- Department of Materials Science and Engineering, KTH Royal Institute of Technology, Brinellv. 23, 10044 Stockholm, Sweden
| | - Peisheng Wang
- Materials Science and Engineering Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8555, Gaithersburg, MD 20899-8555 USA
- Center for Hierarchical Materials Design (CHiMaD), Northwestern University, 2205 Tech Drive, Evanston, IL 60208 USA
| | - Ursula R. Kattner
- Materials Science and Engineering Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8555, Gaithersburg, MD 20899-8555 USA
| | - Carelyn E. Campbell
- Materials Science and Engineering Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8555, Gaithersburg, MD 20899-8555 USA
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The α → ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion. METALS 2017. [DOI: 10.3390/met8010001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Molecular Dynamics Simulations of Shock Loading of Materials: A Review and Tutorial. REVIEWS IN COMPUTATIONAL CHEMISTRY 2017. [DOI: 10.1002/9781119356059.ch2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Laurila T, Sainio S, Jiang H, Isoaho N, Koehne JE, Etula J, Koskinen J, Meyyappan M. Application-Specific Catalyst Layers: Pt-Containing Carbon Nanofibers for Hydrogen Peroxide Detection. ACS OMEGA 2017; 2:496-507. [PMID: 30023609 PMCID: PMC6044567 DOI: 10.1021/acsomega.6b00441] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 01/25/2017] [Indexed: 06/08/2023]
Abstract
Complete removal of metal catalyst particles from carbon nanofibers (CNFs) and other carbon nanostructures is extremely difficult, and the envisioned applications may be compromised by the left-over impurities. To circumvent these problems, one should use, wherever possible, such catalyst materials that are meant to remain in the structure and have some application-specific role, making any removal steps unnecessary. Thus, as a proof-of-concept, we present here a nanocarbon-based material platform for electrochemical hydrogen peroxide measurement utilizing a Pt catalyst layer to grow CNFs with intact Pt particles at the tips of the CNFs. Backed by careful scanning transmission electron microscopy analysis, we show that this material can be readily realized with the Pt catalyst layer thickness impacting the resulting structure and also present a growth model to explain the evolution of the different types of structures. In addition, we show by electrochemical analysis that the material exhibits characteristic features of Pt in cyclic voltammetry and it can detect very small amounts of hydrogen peroxide with very fast response times. Thus, the present sensor platform provides an interesting electrode material with potential for biomolecule detection and in fuel cells and batteries. In the wider range, we propose a new approach where the selection of catalytic particles used for carbon nanostructure growth is made so that (i) they do not need to be removed and (ii) they will have essential role in the final application.
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Affiliation(s)
- Tomi Laurila
- Department
of Electrical Engineering and Automation, School of Electrical Engineering, Aalto University, Tietotie 3, Espoo 02150, Finland
| | - Sami Sainio
- Department
of Electrical Engineering and Automation, School of Electrical Engineering, Aalto University, Tietotie 3, Espoo 02150, Finland
| | - Hua Jiang
- Department
of Applied Physics, School of Science, Aalto
University, Puumiehenkuja
2, Espoo 02150, Finland
| | - Noora Isoaho
- Department
of Electrical Engineering and Automation, School of Electrical Engineering, Aalto University, Tietotie 3, Espoo 02150, Finland
| | - Jessica E. Koehne
- Center
for Nanotechnology, NASA Ames Research Center, Moffett Field, Mountain View, California 94035, United States
| | - Jarkko Etula
- Department
of Chemistry and Materials Science, School of Chemical Technology, Aalto University, Kemistintie 1, Espoo 02150, Finland
| | - Jari Koskinen
- Department
of Chemistry and Materials Science, School of Chemical Technology, Aalto University, Kemistintie 1, Espoo 02150, Finland
| | - M. Meyyappan
- Center
for Nanotechnology, NASA Ames Research Center, Moffett Field, Mountain View, California 94035, United States
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Hazell PJ, Appleby-Thomas GJ, Wielewski E, Escobedo JP. The shock and spall response of three industrially important hexagonal close-packed metals: magnesium, titanium and zirconium. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130204. [PMID: 25071240 DOI: 10.1098/rsta.2013.0204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Magnesium, titanium and zirconium and their alloys are extensively used in industrial and military applications where they would be subjected to extreme environments of high stress and strain-rate loading. Their hexagonal close-packed (HCP) crystal lattice structures present interesting challenges for optimizing their mechanical response under such loading conditions. In this paper, we review how these materials respond to shock loading via plate-impact experiments. We also discuss the relationship between a heterogeneous and anisotropic microstructure, typical of HCP materials, and the directional dependency of the elastic limit and, in some cases, the strength prior to failure.
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Affiliation(s)
- P J Hazell
- School of Engineering and Information Technology, UNSW Canberra at the Australian Defence Force Academy, UNSW Australia, Northcott Drive, Canberra, ACT 2600, Australia
| | - G J Appleby-Thomas
- Centre for Defence Engineering, Cranfield University, Defence Academy of the United Kingdom, Shrivenham, Swindon SN6 8LA, UK
| | - E Wielewski
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - J P Escobedo
- School of Engineering and Information Technology, UNSW Canberra at the Australian Defence Force Academy, UNSW Australia, Northcott Drive, Canberra, ACT 2600, Australia
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Ming LC, Manghnani MH. Isothermal compression and phase transition in beryllium to 28.3 GPa. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0305-4608/14/1/001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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