1
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Cook DH, Kumar P, Payne MI, Belcher CH, Borges P, Wang W, Walsh F, Li Z, Devaraj A, Zhang M, Asta M, Minor AM, Lavernia EJ, Apelian D, Ritchie RO. Kink bands promote exceptional fracture resistance in a NbTaTiHf refractory medium-entropy alloy. Science 2024; 384:178-184. [PMID: 38603511 DOI: 10.1126/science.adn2428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 03/06/2024] [Indexed: 04/13/2024]
Abstract
Single-phase body-centered cubic (bcc) refractory medium- or high-entropy alloys can retain compressive strength at elevated temperatures but suffer from extremely low tensile ductility and fracture toughness. We examined the strength and fracture toughness of a bcc refractory alloy, NbTaTiHf, from 77 to 1473 kelvin. This alloy's behavior differed from that of comparable systems by having fracture toughness over 253 MPa·m1/2, which we attribute to a dynamic competition between screw and edge dislocations in controlling the plasticity at a crack tip. Whereas the glide and intersection of screw and mixed dislocations promotes strain hardening controlling uniform deformation, the coordinated slip of <111> edge dislocations with {110} and {112} glide planes prolongs nonuniform strain through formation of kink bands. These bands suppress strain hardening by reorienting microscale bands of the crystal along directions of higher resolved shear stress and continually nucleate to accommodate localized strain and distribute damage away from a crack tip.
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Affiliation(s)
- David H Cook
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Punit Kumar
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Madelyn I Payne
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Calvin H Belcher
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Pedro Borges
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Wenqing Wang
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Flynn Walsh
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Zehao Li
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Arun Devaraj
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Mingwei Zhang
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Mark Asta
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Andrew M Minor
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Enrique J Lavernia
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Diran Apelian
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Robert O Ritchie
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
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2
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El-Azab SA, Zhang C, Jiang S, Vyatskikh AL, Valdevit L, Lavernia EJ, Schoenung JM. In situ observation of melt pool evolution in ultrasonic vibration-assisted directed energy deposition. Sci Rep 2023; 13:17705. [PMID: 37848463 PMCID: PMC10582076 DOI: 10.1038/s41598-023-44108-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 10/03/2023] [Indexed: 10/19/2023] Open
Abstract
The presence of defects, such as pores, in materials processed using additive manufacturing represents a challenge during the manufacturing of many engineering components. Recently, ultrasonic vibration-assisted (UV-A) directed energy deposition (DED) has been shown to reduce porosity, promote grain refinement, and enhance mechanical performance in metal components. Whereas it is evident that the formation of such microstructural features is affected by the melt pool behavior, the specific mechanisms by which ultrasonic vibration (UV) influences the melt pool remain elusive. In the present investigation, UV was applied in situ to DED of 316L stainless steel single tracks and bulk parts. For the first time, high-speed video imaging and thermal imaging were implemented in situ to quantitatively correlate the application of UV to melt pool evolution in DED. Extensive imaging data were coupled with in-depth microstructural characterization to develop a statistically robust dataset describing the observed phenomena. Our findings show that UV increases the melt pool peak temperature and dimensions, while improving the wettability of injected particles with the melt pool surface and reducing particle residence time. Near the substrate, we observe that UV results in a 92% decrease in porosity, and a 54% decrease in dendritic arm spacing. The effect of UV on the melt pool is caused by the combined mechanisms of acoustic cavitation, ultrasound absorption, and acoustic streaming. Through in situ imaging we demonstrate quantitatively that these phenomena, acting simultaneously, effectively diminish with increasing build height and size due to acoustic attenuation, consequently decreasing the positive effect of implementing UV-A DED. Thus, this research provides valuable insight into the value of in situ imaging, as well as the effects of UV on DED melt pool dynamics, the stochastic interactions between the melt pool and incoming powder particles, and the limitations of build geometry on the UV-A DED technique.
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Affiliation(s)
- Salma A El-Azab
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Cheng Zhang
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Sen Jiang
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Aleksandra L Vyatskikh
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Lorenzo Valdevit
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Enrique J Lavernia
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Julie M Schoenung
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA.
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3
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Jiang L, Gong M, Wang J, Pan Z, Wang X, Zhang D, Wang YM, Ciston J, Minor AM, Xu M, Pan X, Rupert TJ, Mahajan S, Lavernia EJ, Beyerlein IJ, Schoenung JM. Visualization and validation of twin nucleation and early-stage growth in magnesium. Nat Commun 2022; 13:20. [PMID: 35013175 PMCID: PMC8748725 DOI: 10.1038/s41467-021-27591-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 10/25/2021] [Indexed: 11/09/2022] Open
Abstract
The abrupt occurrence of twinning when Mg is deformed leads to a highly anisotropic response, making it too unreliable for structural use and too unpredictable for observation. Here, we describe an in-situ transmission electron microscopy experiment on Mg crystals with strategically designed geometries for visualization of a long-proposed but unverified twinning mechanism. Combining with atomistic simulations and topological analysis, we conclude that twin nucleation occurs through a pure-shuffle mechanism that requires prismatic-basal transformations. Also, we verified a crystal geometry dependent twin growth mechanism, that is the early-stage growth associated with instability of plasticity flow, which can be dominated either by slower movement of prismatic-basal boundary steps, or by faster glide-shuffle along the twinning plane. The fundamental understanding of twinning provides a pathway to understand deformation from a scientific standpoint and the microstructure design principles to engineer metals with enhanced behavior from a technological standpoint.
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Affiliation(s)
- Lin Jiang
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA.,Materials & Structural Analysis Division, Thermo Fisher Scientific, Hillsboro, OR, 97124, USA
| | - Mingyu Gong
- State Key Lab of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Jian Wang
- Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Zhiliang Pan
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA
| | - Xin Wang
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA
| | - Dalong Zhang
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA
| | - Y Morris Wang
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Jim Ciston
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94701, USA
| | - Andrew M Minor
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94701, USA.,Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Mingjie Xu
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA
| | - Xiaoqing Pan
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA.,Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Timothy J Rupert
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA
| | - Subhash Mahajan
- Department of Materials Science and Engineering, University of California, Davis, CA, 95616, USA
| | | | - Irene J Beyerlein
- Department of Mechanical Engineering and Materials, University of California, Santa Barbara, CA, 93101, USA
| | - Julie M Schoenung
- Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA.
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4
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Hu Y, Turlo V, Beyerlein IJ, Mahajan S, Lavernia EJ, Schoenung JM, Rupert TJ. Embracing the Chaos: Alloying Adds Stochasticity to Twin Embryo Growth. Phys Rev Lett 2020; 125:205503. [PMID: 33258657 DOI: 10.1103/physrevlett.125.205503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/03/2020] [Accepted: 10/08/2020] [Indexed: 06/12/2023]
Abstract
High-throughput atomistic simulations reveal the unique effect of solute atoms on twin variant selection in Mg-Al alloys. Twin embryo growth first undergoes a stochastic incubation stage when embryos choose which twin variant to adopt, and then a deterministic growth stage when embryos expand without changing the selected twin variant. An increase in Al composition promotes the stochastic incubation behavior on the atomic level due to nucleation and pinning of interfacial disconnections. At compositions above a critical value, disconnection pinning results in multiple twin variant selection.
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Affiliation(s)
- Yang Hu
- Department of Materials Science and Engineering, University of California, Irvine, California 92697, USA
| | - Vladyslav Turlo
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697, USA
| | - Irene J Beyerlein
- Mechanical Engineering Department, University of California, Santa Barbara, California 93106, USA
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Subhash Mahajan
- Department of Materials Science and Engineering, University of California, Davis, California 95616, USA
| | - Enrique J Lavernia
- Department of Materials Science and Engineering, University of California, Irvine, California 92697, USA
| | - Julie M Schoenung
- Department of Materials Science and Engineering, University of California, Irvine, California 92697, USA
| | - Timothy J Rupert
- Department of Materials Science and Engineering, University of California, Irvine, California 92697, USA
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697, USA
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5
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Ding Z, Zhao G, Sun H, Li S, Ma F, Lavernia EJ, Zhu Y, Liu W. Alloying effects on the plasticity of magnesium: comprehensive analysis of influences of all five slip systems. J Phys Condens Matter 2020; 32:015401. [PMID: 31519010 DOI: 10.1088/1361-648x/ab445d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Low plasticity has been a major issue for the application of Mg alloys. Here, based on the generalized stacking fault energy curves and Arrhenius equation, we systematically study alloying effects on the stacking fault energies and the activation probability of basal and non-basal 〈a〉, and pyramidal 〈c + a〉 slip systems in twenty-one Mg alloys. Our results reveal that activation of 〈c + a〉 slip systems on pyramidal II plane can significantly improve the plasticity. For example, Ca is found to promote the activation probability of this slip system by one order of magnitude and dramatically improve the plasticity of Mg.
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Affiliation(s)
- Zhigang Ding
- Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, People's Republic of China
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6
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Cao C, Yao G, Jiang L, Sokoluk M, Wang X, Ciston J, Javadi A, Guan Z, De Rosa I, Xie W, Lavernia EJ, Schoenung JM, Li X. Bulk ultrafine grained/nanocrystalline metals via slow cooling. Sci Adv 2019; 5:eaaw2398. [PMID: 31467973 PMCID: PMC6707776 DOI: 10.1126/sciadv.aaw2398] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 07/16/2019] [Indexed: 06/10/2023]
Abstract
Cooling, nucleation, and phase growth are ubiquitous processes in nature. Effective control of nucleation and phase growth is of significance to yield refined microstructures with enhanced performance for materials. Recent studies reveal that ultrafine grained (UFG)/nanocrystalline metals exhibit extraordinary properties. However, conventional microstructure refinement methods, such as fast cooling and inoculation, have reached certain fundamental limits. It has been considered impossible to fabricate bulk UFG/nanocrystalline metals via slow cooling. Here, we report a new discovery that nanoparticles can refine metal grains to ultrafine/nanoscale by instilling a continuous nucleation and growth control mechanism during slow cooling. The bulk UFG/nanocrystalline metal with nanoparticles also reveals an unprecedented thermal stability. This method overcomes the grain refinement limits and may be extended to any other processes that involve cooling, nucleation, and phase growth for widespread applications.
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Affiliation(s)
- Chezheng Cao
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Gongcheng Yao
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Lin Jiang
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA 96297, USA
- Materials & Structural Analysis, Thermo Fisher Scientific, Hillsboro, OR 97124, USA
| | - Maximilian Sokoluk
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Xin Wang
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA 96297, USA
| | - Jim Ciston
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Abdolreza Javadi
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Zeyi Guan
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Igor De Rosa
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Weiguo Xie
- Camborne School of Mines, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, UK
| | - Enrique J. Lavernia
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA 96297, USA
| | - Julie M. Schoenung
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA 96297, USA
| | - Xiaochun Li
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
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7
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Derimow N, Santodonato LJ, MacDonald BE, Le B, Lavernia EJ, Abbaschian R. In-Situ Imaging of Molten High-Entropy Alloys Using Cold Neutrons. J Imaging 2019; 5:29. [PMID: 34460477 PMCID: PMC8320920 DOI: 10.3390/jimaging5020029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 02/10/2019] [Accepted: 02/13/2019] [Indexed: 11/17/2022] Open
Abstract
Real-time neutron imaging was utilized to produce a movie-like series of radiographs for in-situ observation of the remixing of liquid state immiscibility that occurs in equiatomic CoCrCu with the addition of Ni. A previous neutron imaging study demonstrated that liquid state immiscibility can be observed in-situ for the equiatomic CoCrCu alloy. In this follow-up study, equiatomic buttons of CoCrCu were placed alongside small Ni buttons inside an alumina crucible in a high-temperature vacuum furnace. The mass of the Ni buttons was specifically selected such that when melted in the same crucible as the CoCrCu buttons, the overall composition would become equiatomic CoCrCuNi. Neutron imaging was simultaneously carried out to capture 10 radiographs in 20 °C steps from 1000 °C to 1500 °C and back down to 1000 °C. This, in turn, produced a movie-like series of radiographs that allow for the observation of the buttons melting, the transition from immiscible to miscible as Ni is alloyed into the CoCrCu system, and solidification. This novel imaging process showed the phase-separated liquids remixing into a single-phase liquid when Ni dissolves into the melt, which makes this technique crucial for understanding the liquid state behavior of these complex alloy systems. As metals are not transparent to X-ray imaging techniques at this scale, neutron imaging of melting and solidification allows for the observation of liquid state phase changes in real time. Thermodynamic calculations of the isopleth for CoCrCuNix were carried out to compare the observed results to the predictions resulting from the current Thermo-Calc TCHEA3 thermodynamic database. The calculations show a very good agreement with the experimental results, as the calculations indicate that the CoCrCuNix alloy solidifies from a single-phase liquid when x ≥ 0.275, which is close to the nominal concentration of the CoCrCuNi alloy (x = 0.25). The neutron imaging shows that the solidification of CoCrCuNi results from a single-phase liquid. This is evident as no changes in the neutron attenuation were observed during the solidification of the CoCrCuNi alloy.
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Affiliation(s)
- Nicholas Derimow
- Materials Science & Engineering Department, University of California, Riverside, CA 92521, USA
| | | | - Benjamin E. MacDonald
- Materials Science & Engineering Department, University of California, Irvine, CA 92697, USA
| | - Bryan Le
- Materials Science & Engineering Department, University of California, Riverside, CA 92521, USA
| | - Enrique J. Lavernia
- Materials Science & Engineering Department, University of California, Irvine, CA 92697, USA
| | - Reza Abbaschian
- Materials Science & Engineering Department, University of California, Riverside, CA 92521, USA
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8
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Fu Z, Jiang L, Wardini JL, MacDonald BE, Wen H, Xiong W, Zhang D, Zhou Y, Rupert TJ, Chen W, Lavernia EJ. A high-entropy alloy with hierarchical nanoprecipitates and ultrahigh strength. Sci Adv 2018; 4:eaat8712. [PMID: 30333993 PMCID: PMC6184785 DOI: 10.1126/sciadv.aat8712] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 09/07/2018] [Indexed: 05/23/2023]
Abstract
High-entropy alloys (HEAs) are a class of metallic materials that have revolutionized alloy design. They are known for their high compressive strengths, often greater than 1 GPa; however, the tensile strengths of most reported HEAs are limited. Here, we report a strategy for the design and fabrication of HEAs that can achieve ultrahigh tensile strengths. The proposed strategy involves the introduction of a high density of hierarchical intragranular nanoprecipitates. To establish the validity of this strategy, we designed and fabricated a bulk Fe25Co25Ni25Al10Ti15 HEA to consist of a principal face-centered cubic (fcc) phase containing hierarchical intragranular nanoprecipitates. Our results show that precipitation strengthening, as one of the main strengthening mechanisms, contributes to a tensile yield strength (σ0.2) of ~1.86 GPa and an ultimate tensile strength of ~2.52 GPa at room temperature, which heretofore represents the highest strength reported for an HEA with an appreciable failure strain of ~5.2%.
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Affiliation(s)
- Zhiqiang Fu
- Guangdong Key Laboratory for Advanced Metallic Materials Processing, South China University of Technology, Guangzhou, Guangdong 510640, China
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
| | - Lin Jiang
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
- Materials and Structural Analysis, Thermo Fisher Scientific, Hillsboro, OR 97124, USA
| | - Jenna L. Wardini
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
| | - Benjamin E. MacDonald
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
| | - Haiming Wen
- Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA
| | - Wei Xiong
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Dalong Zhang
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
| | - Yizhang Zhou
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
| | - Timothy J. Rupert
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
| | - Weiping Chen
- Guangdong Key Laboratory for Advanced Metallic Materials Processing, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Enrique J. Lavernia
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, USA
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9
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Wu C, Ma K, Zhang D, Wu J, Xiong S, Luo G, Zhang J, Chen F, Shen Q, Zhang L, Lavernia EJ. Precipitation phenomena in Al-Zn-Mg alloy matrix composites reinforced with B 4C particles. Sci Rep 2017; 7:9589. [PMID: 28852113 PMCID: PMC5575324 DOI: 10.1038/s41598-017-10291-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 08/07/2017] [Indexed: 11/13/2022] Open
Abstract
To provide insight into precipitation phenomena in age-hardening Al-Zn-Mg(-Cu) matrix composites, an Al 7075 alloy composite reinforced with B4C particles was selected as a model system. The bulk composites were fabricated via plasma activated sintering and followed by a peak aged (T6) heat treatment. Two types of Al matrix zones were identified in the composite: (1) the regions in the vicinity of the matrix/reinforcement interface, defined as “matrix plastic zone” (MPZ) hereafter, and (2) the regions away from the matrix/reinforcement interface, simply defined as matrix hereafter. The precipitation behavior in the MPZ was characterized and compared to that in the matrix. The MPZ contained a high density of dislocations. The number density of GP zones in the MPZ is lower than that in the matrix while the average size of the GP zones in MPZ is coarser. In addition, semi-coherent platelet η′ precipitates were observed but only in the MPZ. The dislocations and the Al/B4C interfaces provide more heterogeneous nucleation sites for the η′ precipitates in the MPZ. The growth and coarsening of the η′ precipitates caused rapid depletion of Mg and Zn solute atoms in the MPZ.
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Affiliation(s)
- Chuandong Wu
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China.,Department of Chemical Engineering and Materials Science, University of California-Irvine, Irvine, CA, 92697, USA
| | - Kaka Ma
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Dalong Zhang
- Department of Chemical Engineering and Materials Science, University of California-Irvine, Irvine, CA, 92697, USA.,Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN, 37831, USA
| | - Jialu Wu
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Shuya Xiong
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Guoqiang Luo
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Jian Zhang
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Fei Chen
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Qiang Shen
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China.
| | - Lianmeng Zhang
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Enrique J Lavernia
- Department of Chemical Engineering and Materials Science, University of California-Irvine, Irvine, CA, 92697, USA.
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10
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Yang S, Chen F, Shen Q, Lavernia EJ, Zhang L. Microstructure and Electrical Properties of AZO/Graphene Nanosheets Fabricated by Spark Plasma Sintering. Materials (Basel) 2016; 9:ma9080638. [PMID: 28773759 PMCID: PMC5509084 DOI: 10.3390/ma9080638] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 06/17/2016] [Accepted: 07/20/2016] [Indexed: 12/02/2022]
Abstract
In this study we report on the sintering behavior, microstructure and electrical properties of Al-doped ZnO ceramics containing 0–0.2 wt. % graphene sheets (AZO-GNSs) and processed using spark plasma sintering (SPS). Our results show that the addition of <0.25 wt. % GNSs enhances both the relative density and the electrical resistivity of AZO ceramics. In terms of the microstructure, the GNSs are distributed at grain boundaries. In addition, the GNSs are also present between ZnO and secondary phases (e.g., ZnAl2O4) and likely contribute to the measured enhancement of Hall mobility (up to 105.1 cm2·V−1·s−1) in these AZO ceramics. The minimum resistivity of the AZO-GNS composite ceramics is 3.1 × 10−4 Ω·cm which compares favorably to the value of AZO ceramics which typically have a resistivity of 1.7 × 10−3 Ω·cm.
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Affiliation(s)
- Shuang Yang
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
| | - Fei Chen
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
| | - Qiang Shen
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
| | - Enrique J Lavernia
- Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA.
| | - Lianmeng Zhang
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
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Jiang L, Hu T, Yang H, Zhang D, Topping T, Lavernia EJ, Schoenung JM. Deformation of a ceramic/metal interface at the nanoscale. Nanoscale 2016; 8:10541-10547. [PMID: 27147300 DOI: 10.1039/c6nr02011a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The mechanical response of heterophase interfaces has attracted substantial attention in recent years. Here, we utilized an in situ transmission electron microscopy (TEM) technique to isolate an individual nanoscale ceramic/metal interface and characterize its nanomechanical response. The interface, at which there was a Mg-rich segregation nanolayer between the single crystal ceramic (B4C) and the polycrystalline metal (Al alloy, AA5083), was determined to have a bond strength greater than 1.5 GPa. Bimodal failure and metallic grain rotation occurred in the metallic region, allowing the interface to accommodate a deformation strain of 5.4%. The roles of elemental segregation and nanoscale dimensions on interfacial debonding mechanisms are discussed.
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Affiliation(s)
- Lin Jiang
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92697, USA and Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA.
| | - Tao Hu
- Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA. and Department of NanoEngineering, University of California, San Diego, CA 92093, USA
| | - Hanry Yang
- Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA. and School of Mechanical and Materials Engineering, Washington State University, WA 99164, USA
| | - Dalong Zhang
- Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA.
| | - Troy Topping
- Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA. and Department of Mechanical Engineering, California State University, Sacramento, Sacramento, CA 95819, USA
| | - Enrique J Lavernia
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92697, USA and Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA.
| | - Julie M Schoenung
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92697, USA and Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA.
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Wen H, Lin Y, Seidman DN, Schoenung JM, van Rooyen IJ, Lavernia EJ. An Efficient and Cost-Effective Method for Preparing Transmission Electron Microscopy Samples from Powders. Microsc Microanal 2015; 21:1184-1194. [PMID: 26350148 DOI: 10.1017/s1431927615014695] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The preparation of transmission electron microcopy (TEM) samples from powders with particle sizes larger than ~100 nm poses a challenge. The existing methods are complicated and expensive, or have a low probability of success. Herein, we report a modified methodology for preparation of TEM samples from powders, which is efficient, cost-effective, and easy to perform. This method involves mixing powders with an epoxy on a piece of weighing paper, curing the powder-epoxy mixture to form a bulk material, grinding the bulk to obtain a thin foil, punching TEM discs from the foil, dimpling the discs, and ion milling the dimpled discs to electron transparency. Compared with the well established and robust grinding-dimpling-ion-milling method for TEM sample preparation for bulk materials, our modified approach for preparing TEM samples from powders only requires two additional simple steps. In this article, step-by-step procedures for our methodology are described in detail, and important strategies to ensure success are elucidated. Our methodology has been applied successfully for preparing TEM samples with large thin areas and high quality for many different mechanically milled metallic powders.
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Affiliation(s)
- Haiming Wen
- 1Department of Chemical Engineering and Materials Science,University of California at Davis,Davis,CA 95616,USA
| | - Yaojun Lin
- 4State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering,Yanshan University,Qinhuangdao,Hebei 066004,P.R. China
| | - David N Seidman
- 2Department of Materials Science and Engineering,Northwestern University,Evanston,IL 60208-3108,USA
| | - Julie M Schoenung
- 1Department of Chemical Engineering and Materials Science,University of California at Davis,Davis,CA 95616,USA
| | - Isabella J van Rooyen
- 3Idaho National Laboratory,Fuel Performance and Design Department,Idaho Falls,ID 83415-6188,USA
| | - Enrique J Lavernia
- 1Department of Chemical Engineering and Materials Science,University of California at Davis,Davis,CA 95616,USA
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Xie KY, Wang Y, Zhao Y, Chang L, Wang G, Chen Z, Cao Y, Liao X, Lavernia EJ, Valiev RZ, Sarrafpour B, Zoellner H, Ringer SP. Nanocrystalline β-Ti alloy with high hardness, low Young's modulus and excellent in vitro biocompatibility for biomedical applications. Materials Science and Engineering: C 2013; 33:3530-6. [DOI: 10.1016/j.msec.2013.04.044] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/28/2013] [Accepted: 04/22/2013] [Indexed: 11/28/2022]
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Abstract
AbstractThe tensile behavior of bimodal nanocrystalline Al-7.5Mg alloys was investigated using experiments and two-dimensional axisymmetric elastic-plastic finite element method (FEM). Cryomilled nanocrystalline powders blended with 15% and 30% unmilled coarse-grained powders were consolidated by hot isostatic pressing followed by extrusion to produce bulk bimodal nanocrystalline Al-7.5Mg alloys, which were comprised of nanocrystalline grains separated by coarse-grain regions. The calculated stress-strain curves have acceptable agreement with experimental curves of the bimodal structures. The bimodal Al-7.5Mg alloys show reasonable ductility while retaining enhanced strength compared to conventional alloys and nanocrystalline metals.
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Liddicoat PV, Liao XZ, Zhao Y, Zhu Y, Murashkin MY, Lavernia EJ, Valiev RZ, Ringer SP. Nanostructural hierarchy increases the strength of aluminium alloys. Nat Commun 2010; 1:63. [DOI: 10.1038/ncomms1062] [Citation(s) in RCA: 469] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 08/06/2010] [Indexed: 11/09/2022] Open
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Cheng S, Zhao Y, Wang Y, Li Y, Wang XL, Liaw PK, Lavernia EJ. Structure modulation driven by cyclic deformation in nanocrystalline NiFe. Phys Rev Lett 2010; 104:255501. [PMID: 20867394 DOI: 10.1103/physrevlett.104.255501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Indexed: 05/29/2023]
Abstract
Theoretical modeling suggests that the grain size remains unchanged during fatigue crack growth in nanocrystalline metals. Here we demonstrate that a modulated structure is generated in a nanocrystalline Ni-Fe alloy under cyclic deformation. Substantial grain coarsening and loss of growth twins are observed in the path of fatigue cracks, while the grains away from the cracks remain largely unaffected. Statistical analyses suggest that the grain coarsening is realized through the grain lattice rotation and coalescence and the loss of growth twins may be related to the detwinning process near crack tip.
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Affiliation(s)
- Sheng Cheng
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA.
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Cheng S, Zhao Y, Guo Y, Li Y, Wei Q, Wang XL, Ren Y, Liaw PK, Choo H, Lavernia EJ. High Plasticity and Substantial Deformation in Nanocrystalline NiFe Alloys Under Dynamic Loading. Adv Mater 2009; 21:5001-5004. [PMID: 25378188 DOI: 10.1002/adma.200901991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2009] [Indexed: 06/04/2023]
Abstract
A nanocrystalline (NC) NiFe alloy is presented, in which both highly improved plasticity and strength are achieved by the dynamic-loading-induced deformation mechanisms of de-twinning (that is, reduction of twin density) and significant grain coarsening. This work highlights potential ingenious avenues to exploit the superior behavior of NC materials under extreme conditions.
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Affiliation(s)
- Sheng Cheng
- Department of Materials Science and Engineering University of Tennessee Knoxville, TN 37996 (USA)
| | - Yonghao Zhao
- Department of Chemical Engineering and Materials Science University of California Davis, CA 95616 (USA)
| | - Yazhou Guo
- Department of Mechanical Engineering University of North Carolina Charlotte, NC 28223 (USA)
| | - Ying Li
- Department of Chemical Engineering and Materials Science University of California Davis, CA 95616 (USA)
| | - Qiuming Wei
- Department of Mechanical Engineering University of North Carolina Charlotte, NC 28223 (USA)
| | - Xun-Li Wang
- Neutron Scattering Science Division Oak Ridge National Laboratory Oak Ridge, TN 37831 (USA)
| | - Yang Ren
- Advanced Photon Source, Argonne National Laboratory Argonne, IL 60439 (USA)
| | - Peter K Liaw
- Department of Materials Science and Engineering University of Tennessee Knoxville, TN 37996 (USA)
| | - Hahn Choo
- Department of Materials Science and Engineering University of Tennessee Knoxville, TN 37996 (USA)
| | - Enrique J Lavernia
- Department of Chemical Engineering and Materials Science University of California Davis, CA 95616 (USA)
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Wang X, Allen MR, Burr DB, Lavernia EJ, Jeremić B, Fyhrie DP. Identification of material parameters based on Mohr-Coulomb failure criterion for bisphosphonate treated canine vertebral cancellous bone. Bone 2008; 43:775-80. [PMID: 18599390 PMCID: PMC2622738 DOI: 10.1016/j.bone.2008.05.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 05/23/2008] [Accepted: 05/28/2008] [Indexed: 11/28/2022]
Abstract
Nanoindentation has been widely used to study bone tissue mechanical properties. The common method and equations for analyzing nanoindentation, developed by Oliver and Pharr, are based on the assumption that the material is linearly elastic. In the present study, we adjusted the constraint of linearly elastic behavior and use nonlinear finite element analysis to determine the change in cancellous bone material properties caused by bisphosphonate treatment, based on an isotropic form of the Mohr-Coulomb failure model. Thirty-three canine lumbar vertebrae were used in this study. The dogs were treated daily for 1 year with oral doses of alendronate, risedronate, or saline vehicle at doses consistent, on a mg/kg basis, to those used clinically for the treatment of post-menopausal osteoporosis. Two sets of elastic modulus and hardness values were calculated for each specimen using the Continuous Stiffness Measurement (CSM) method (E(CSM) and H(CSM)) from the loading segment and the Oliver-Pharr method (E(O-P) and H(O-P)) from the unloading segment, respectively. Young's modulus (E(FE)), cohesion (c), and friction angle (phi) were identified using a finite element model for each nanoindentation. The bone material properties were compared among groups and between methods for property identification. Bisphosphonate treatment had a significant effect on several of the material parameters. In particular, Oliver-Pharr hardness was larger for both the risedronate- and alendronate-treated groups compared to vehicle and the Mohr-Coulomb cohesion was larger for the risedronate-treated compared to vehicle. This result suggests that bisphosphonate treatment increases the hardness and shear strength of bone tissue. Shear strength was linearly predicted by modulus and hardness measured by the Oliver-Pharr method (r(2)=0.99). These results show that bisphosphonate-induced changes in Mohr-Coulomb material properties, including tissue shear cohesive strength, can be accurately calculated from Oliver-Pharr measurements of Young's modulus and hardness.
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Affiliation(s)
- Xiang Wang
- Lawrence J. Ellison Musculoskeletal Research Center, University of California Davis Medical Center, Sacramento, CA, USA.
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Wu XL, Liao XZ, Srinivasan SG, Zhou F, Lavernia EJ, Valiev RZ, Zhu YT. New deformation twinning mechanism generates zero macroscopic strain in nanocrystalline metals. Phys Rev Lett 2008; 100:095701. [PMID: 18352724 DOI: 10.1103/physrevlett.100.095701] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Indexed: 05/26/2023]
Abstract
Macroscopic strain was hitherto considered a necessary corollary of deformation twinning in coarse-grained metals. Recently, twinning has been found to be a preeminent deformation mechanism in nanocrystalline face-centered-cubic (fcc) metals with medium-to-high stacking fault energies. Here we report a surprising discovery that the vast majority of deformation twins in nanocrystalline Al, Ni, and Cu, contrary to popular belief, yield zero net macroscopic strain. We propose a new twinning mechanism, random activation of partials, to explain this unusual phenomenon. The random activation of partials mechanism appears to be the most plausible mechanism and may be unique to nanocrystalline fcc metals with implications for their deformation behavior and mechanical properties.
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Affiliation(s)
- X L Wu
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
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Wang X, Sudhaker Rao D, Ajdelsztajn L, Ciarelli TE, Lavernia EJ, Fyhrie DP. Human iliac crest cancellous bone elastic modulus and hardness differ with bone formation rate per bone surface but not by existence of prevalent vertebral fracture. J Biomed Mater Res B Appl Biomater 2008; 85:68-77. [PMID: 17696151 DOI: 10.1002/jbm.b.30918] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The goals of this study were to measure tissue-level elastic moduli and hardness of human cancellous bone using nanoindentation, and determine the relationship between nanoindentation results and previously measured bone histomorphometric variables and bone mineralization. Forty iliac crest biopsies were used in this study, which were collected from Caucasian females with vertebral fracture or from a normal healthy female Caucasian population. They were also categorized into two groups according to high or low bone formation rate per bone surface (BFR/BS). Thirty-two sites were randomly selected on each specimen for nanoindentation with a Berkovich diamond indenter. Two sets of elastic moduli and hardness were calculated using the continuous stiffness measurement method and the Oliver-Pharr method, respectively. Relationships between nanoindentation results and donor age, bone mineralization, and histomorphometric variables were examined. No difference in elastic moduli or hardness was observed between the normal and fracture groups. Significantly lower elastic moduli were observed in the high BFR/BS group. The elastic moduli and hardness measurements were not significantly correlated with the bone mineralization measured independently in a previous study. Linear correlation between elastic modulus and hardness calculated using the Oliver-Pharr method was not different between the normal and fracture groups or between the high and low BFR/BS groups. Nanoindentation hardness was a very good predictor of bone tissue elastic modulus for both normal and osteoporotic bone tissues. Osteoporosis may not change the relationship between bone tissue elastic modulus, bone hardness, and bone mineralization.
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Affiliation(s)
- Xiang Wang
- Lawrence J. Ellison Musculoskeletal Research Center, University of California Davis Medical Center, Room 2000, Research Facility I, 4635 Second Avenue, Sacramento, California 95817, USA.
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Abstract
BACKGROUND AND OBJECTIVES Few quantitative studies have investigated the temperature dependent viscoelastic properties of cartilage tissue. Cartilage softens and can be reshaped when heated using laser, RF, or contact heating sources. The objectives of this study were to: (1) measure temperature dependent flexural storage moduli and mechanical relaxation in cartilage, (2) determine the impact of tissue water content and orientation on these mechanical properties, and (3) use these measurements to estimate the activation energy associated with the mechanical relaxation process. STUDY DESIGN/MATERIALS AND METHODS Porcine nasal septal cartilage specimens (30 x 10 x 2 mm) were deformed using a single cantilever arrangement in a dynamic thermomechanical analyzer. Stress relaxation measurements were made at discrete temperatures ranging from 25 to 70 degrees C in response to cyclic deformation (within the linear viscoelastic region). The time and temperature dependent behavior of cartilage was measured using frequency multiplexing techniques (10-64 Hz), and these results were used to estimate the activation energy for the phase change using the Williams-Landel-Ferry (WLF) equation and the Arrhenius kinetic equation. In addition, the effect of tissue orientation was examined with specimens oriented in both transverse and longitudinal directions at room temperature. RESULTS The storage moduli of porcine cartilage decreased with increasing temperature, and a critical change in mechanical properties was observed between 58 and 60 degrees C with a reduction in the storage modulus by 85-90%. The shift of the stress relaxation behavior from viscoelastic solid to viscoelastic liquid was observed between 50 and 57 degrees C and likely corresponds to the transition temperature region in which structural changes in the tissue occur. The storage moduli for transverse and longitudinally oriented specimens were 19-22 and 14-16 MPa, respectively at ambient temperature. Reducing the water content (<10% mass loss) by allowing it to dry under ambient conditions resulted in reduction in the storage modulus by 31-36%. The activation energy associated with the mechanical relaxation of cartilage was 147 kJ/mole at 60 degrees C. This value was calculated by measuring stress-strain relationship under conditions where linear viscoelastic behavior was observed (0.09-0.15% of strain) within the transition temperature region (58-60 degrees C). CONCLUSIONS The anisotropic mechanical behavior of cartilage was quantitatively analyzed in the transversely and longitudinally oriented specimens. Viscoelastic behavior appeared to be strongly dependent on the water content. Using empirically determined estimates of the transition zone temperature range accompanying stress relaxation, the activation energy for stress relaxation was calculated using time and temperature superposition theory and WLF equation. Further investigation of the molecular changes, which occur during laser irradiation, may assist in understanding the thermal and mechanical behavior of cartilage and how the reshaping process might to be optimized.
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Affiliation(s)
- YongSeok Chae
- Department of Chemical Engineering and Materials Science, The Henry Samueli School of Engineering, University of California, Irvine, California 92697-2575, USA
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Svaasand LO, Randeberg LL, Aguilar G, Majaron B, Kimel S, Lavernia EJ, Nelson JS. Cooling efficiency of cryogen spray during laser therapy of skin. Lasers Surg Med 2003; 32:137-42. [PMID: 12561047 DOI: 10.1002/lsm.10120] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND AND OBJECTIVES Cryogen spray cooling (CSC) is used extensively for epidermal protection during laser-induced photothermolysis of port wine stains and other vascular skin lesions. The efficacy of CSC depends critically on the heat transfer coefficient (H) at the skin surface for which, however, no reliable values exist. Reported values for H, based on tissue phantoms, vary from 1,600 to 60,000 W/m(2) K. STUDY DESIGN/MATERIALS AND METHODS A simple experimental model was designed and constructed, consisting of a pure silver-measuring disk (diameter 10 mm, thickness approximately 1 mm), embedded in a thermal insulator. The disk was covered with a 10 microm thick stratum corneum layer, detached from in vivo human skin. The heat transfer coefficient of the stratum corneum/cryogen interface was measured during CSC with short spurts of atomized tetrafluoroethane. RESULTS H was found to be dependent on the specific design of the cryogen valve and nozzle. With nozzles used in typical clinical settings, H was 11,500 W/m(2) K, when averaged over a 100 ms spurt, and 8,000 W/m(2) K when averaged over a 200 ms spurt. CONCLUSIONS The presented model enables accurate prediction of H and thus improve control over temperature depth profile and cooling efficiency during laser therapy. Thereby, it may contribute to improvement of therapeutic outcome.
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Affiliation(s)
- L O Svaasand
- Norwegian University of Science and Technology, Trondheim, Norway.
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Aguilar G, Majaron B, Karapetian E, Lavernia EJ, Nelson JS. Experimental study of cryogen spray properties for application in dermatologic laser surgery. IEEE Trans Biomed Eng 2003; 50:863-9. [PMID: 12848354 DOI: 10.1109/tbme.2003.813537] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cryogenic sprays are used for cooling human skin during laser dermatologic surgery. In this paper, six straight-tube nozzles are characterized by photographs of cryogenic spray shapes, as well as measurements of average droplet diameter, velocity, and temperature. A single-droplet evaporation model to predict average spray droplet diameter and temperature is tested using the experimental data presented here. The results show two distinct spray patterns--sprays for 1.4-mm-diameter nozzles (wide nozzles) show significantly larger average droplet diameters and higher temperatures as a function of distance from the nozzle compared with those for 0.5-0.8-mm-diameter nozzles (narrow nozzles). These results complement and support previously reported studies, indicating that wide nozzles induce more efficient heat extraction than the narrow nozzles.
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Affiliation(s)
- Guillermo Aguilar
- Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA.
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Aguilar G, Díaz SH, Lavernia EJ, Nelson JS. Cryogen spray cooling efficiency: improvement of port wine stain laser therapy through multiple-intermittent cryogen spurts and laser pulses. Lasers Surg Med 2003; 31:27-35. [PMID: 12124712 DOI: 10.1002/lsm.10076] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND AND OBJECTIVES Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser treatment of port wine stain (PWS) birthmarks. Unfortunately, CSC may not provide the necessary protection for patients with high concentrations of epidermal melanin. The objectives of this study are to: (1) provide a definition of cooling efficiency (eta) based on the amount of heat removed per unit area of skin for a given cooling time; (2) using this definition, establish the eta of previously reported spray nozzles; (3) identify the maximum benefit expected in PWS laser therapy based solely on improvement of eta; and (4) study the feasibility of using multiple-intermittent cryogen spurts and laser pulses to improve PWS laser therapy. STUDY DESIGN/MATERIALS AND METHODS A theoretical definition to quantify eta is introduced. Subsequently, finite difference heat diffusion and Monte Carlo light distribution models are used to study the spatial and temporal temperature distributions in PWS skin considering: (1) the current approach to PWS laser therapy consisting of a single cryogen spurt followed by a single pulsed dye laser exposure (SCS-SLP approach); and (2) multiple cryogen spurts and laser pulses (MCS-MLP approach). At the same time, an Arrhenius-type kinetic model is used to compute the epidermal and PWS thermal damages (Omega(E) and Omega(PWS), respectively) for a high epidermal melanin concentration (20%), corresponding to skin types V-VI. RESULTS The eta corresponding to a wide range of heat transfer coefficients (h) is quantified. For reported CSC nozzle devices eta varies from 40 to 98%. Using the SCS-SLP approach, it is shown that even eta = 100% cannot prevent excessive Omega(E) for a skin types V-VI. In contrast, the MCS-MLP approach provides adequate epidermal protection while permitting PWS photocoagulation for the same skin types. CONCLUSIONS The new proposed definition allows to compute the cooling efficiency of CSC nozzle devices. Computer models have been developed and used to show that the SCS-SLP approach will not provide adequate epidermal protection for darker skin patients (skin types V-VI), even for eta = 100%. In contrast, the MCS-MLP approach may be a viable solution to improve PWS laser therapy for darker skin patients.
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Affiliation(s)
- Guillermo Aguilar
- Center for Biomedical Engineering, Beckman Laser Institute and Medical Clinic, University of California-Irvine, 1002 Health Sciences Road East, Irvine, CA 92697, USA.
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Karapetian E, Aguilar G, Kimel S, Lavernia EJ, Nelson JS. Effects of mass flow rate and droplet velocity on surface heat flux during cryogen spray cooling. Phys Med Biol 2003; 48:N1-6. [PMID: 12564506 DOI: 10.1088/0031-9155/48/1/401] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cryogen spray cooling (CSC) is used to protect the epidermis during dermatologic laser surgery. To date, the relative influence of the fundamental spray parameters on surface cooling remains incompletely understood. This study explores the effects of mass flow rate and average droplet velocity on the surface heat flux during CSC. It is shown that the effect of mass flow rate on the surface heat flux is much more important compared to that of droplet velocity. However, for fully atomized sprays with small flow rates, droplet velocity can make a substantial difference in the surface heat flux.
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Affiliation(s)
- Emil Karapetian
- Department of Chemical Engineering and Material Sciences, University of California, Irvine, CA 92697, USA
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Majaron B, Kimel S, Verkruysse W, Aguilar G, Pope K, Svaasand LO, Lavernia EJ, Nelson JS. Cryogen spray cooling in laser dermatology: effects of ambient humidity and frost formation. Lasers Surg Med 2001; 28:469-76. [PMID: 11413560 DOI: 10.1002/lsm.1076] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND AND OBJECTIVE Dynamics of cryogen spray deposition, water condensation and frost formation is studied in relationship to cooling rate and efficiency of cryogen spray cooling (CSC) in combination with laser dermatologic surgery. STUDY DESIGN/MATERIALS AND METHODS A high-speed video camera was used to image the surface of human skin during and after CSC using a commercial device. The influence of ambient humidity on heat extraction dynamics was measured in an atmosphere-controlled chamber using an epoxy block with embedded thermocouples. RESULTS A layer of liquid cryogen may remain on the skin after the spurt termination and prolong the cooling time well beyond that selected by the user. A layer of frost starts forming only after the liquid cryogen retracts. Condensation of ambient water vapor and subsequent frost formation deposit latent heat to the target site and may significantly impair the CSC cooling rate. CONCLUSIONS Frost formation following CSC does not usually affect laser dosage delivered for therapy of subsurface targets. Moreover, frost formation may reduce the risk of cryo-injury associated with prolonged cooling. The epidermal protection during CSC assisted laser dermatologic surgery can be further improved by eliminating the adverse influence of ambient humidity.
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Affiliation(s)
- B Majaron
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, CA 92612, USA.
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Abstract
Nanocrystalline and conventional Co-Cr (ASTM F75) coatings were prepared by plasma spraying for possible orthopedic implant applications. Scanning electron microscopy and transmission electron microscopy were used to study the macrostructure and microstructure of the resultant sprayed coatings. The corrosion resistance was characterized by an in vitro potentiodynamic anodic polarization technique in a pseudophysiological solution. The nanocrystalline coating has higher porosity, lower corrosion current density, and less localized damage than that of the conventional one, demonstrating better application potential for orthopedic implants. A change in the atomic compositional difference between the grain interior and the grain boundary, the presence of residual strain in the grain interiors, and a change in the repassivation kinetics are discussed as possible explanations for the enhanced corrosion behavior observed.
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Affiliation(s)
- D Cheng
- Department of Chemical and Biochemical Engineering and Materials Science, University of California, Irvine, 92697-2575, USA
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Aguilar G, Majaron B, Pope K, Svaasand LO, Lavernia EJ, Nelson JS. Influence of nozzle-to-skin distance in cryogen spray cooling for dermatologic laser surgery. Lasers Surg Med 2001; 28:113-20. [PMID: 11241516 DOI: 10.1002/lsm.1025] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND OBJECTIVE Cryogen sprays are used for cooling human skin during various laser treatments. Since characteristics of such sprays have not been completely understood, the optimal atomizing nozzle design and operating conditions for cooling human skin remain to be determined. MATERIALS AND METHODS Two commercial cryogenic spray nozzles are characterized by imaging the sprays and the resulting areas on a substrate, as well as by measurements of the average spray droplet diameters, velocities, temperatures, and heat transfer coefficients at the cryogen-substrate interface; all as a function of distance from the nozzle tip. RESULTS Size of spray cones and sprayed areas vary with distance and nozzle. Average droplet diameter and velocity increase with distance in the vicinity of the nozzle, slowly decreasing after a certain maximum is reached. Spray temperature decreases with distance due to the extraction of latent heat of vaporization. At larger distances, temperature increases due to complete evaporation of spray droplets. These three variables combined determine the heat transfer coefficient, which may also initially increase with distance, but eventually decreases as nozzles are moved far from the target. CONCLUSIONS Sprayed areas and heat extraction efficiencies produced by current commercial nozzles may be significantly modified by varying the distance between the nozzle and the sprayed surface.
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Affiliation(s)
- G Aguilar
- Whitaker Center for Biomedical Engineering, University of California, Irvine, California 92697, USA
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Zeng X, Lavernia EJ. Creep behavior of dispersion-strengthened Ni3Al intermetallic processed using reactive atomization and deposition. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0956-716x(95)00063-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Lavernia EJ. Synthesis of Discontinously Reinforced Metal matrix Composites Using Spray Atomisation and Co injection. DEFENCE SCI J 1993. [DOI: 10.14429/dsj.43.4335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Lavernia EJ, Gomez E, Grant N. The structures and properties of MgAlZr and MgZnZr alloys produced by liquid dynamic compaction. ACTA ACUST UNITED AC 1987. [DOI: 10.1016/0025-5416(87)90514-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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