103 results on '"Yunbo Xu"'
Search Results
2. Exploring the mechanism underlying hyperuricemia using comprehensive research on multi-omics
- Author
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Hengrui Liu, Ruolin Xie, Qiongqiong Dai, Ji Fang, Yunbo Xu, and Bo Li
- Subjects
Multidisciplinary - Abstract
Hyperuricemia involves multiple complex metabolisms, but no study has conducted a comprehensive analysis using human blood and urine metabolomics for hyperuricemia. Serum and urine samples from 10 patients with hyperuricemia and 5 controls were collected and analyzed by the UHPLC-MS/MS. Differential metabolites were identified and used in the enrichment analysis where we collected hyperuricemia target genes. Hyperuricemia kidney differential expressed genes (DEGs) were identified using RNA-sequencing data from the hyperuricemia mouse model induced by the potassium oxonate. A Mendelian randomization analysis of the association between caffeine-containing drinks and gout risk was conducted. An intersection analysis between hyperuricemia target genes and hyperuricemia kidney DEGs was conducted and the resulting genes were used for network analysis using the STRING. 227 differential metabolites were identified as differential metabolites and were enriched in 7 KEGG pathways, among which “Caffeine metabolism” was the top. The Mendelian randomization analysis revealed a significant association between tea or coffee intake and gout risk. There were 2173 genes that were identified as hyperuricemia kidney DEGs from mouse data. The intersection analysis identified 51 genes for the hyperuricemia regulation network. A hyperuricemia regulation protein network in the kidney was constructed. This study suggested a potential association between caffeine and hyperuricemia and constructed a hyperuricemia regulation network for future reference.
- Published
- 2023
3. Improvement of strength-ductility combination in ultra-high-strength medium-Mn Q&P steel by tailoring the characteristics of martensite/ retained austenite constituents
- Author
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Jiayu Li, Yunbo Xu, Bing Lu, Yongmei Yu, Yi Jing, and Weihua Sun
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Biomaterials ,Metals and Alloys ,Ceramics and Composites ,Surfaces, Coatings and Films - Published
- 2022
4. Microstructural characterization and mechanical properties in resistance spot welding of Q&P980 steel involving 'effective softening' at the fusion boundary
- Author
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Yi Jing, Yunbo Xu, Dongxiao Wang, Jiayu Li, Yongmei Yu, and Lin Lu
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2023
5. Control of Austenite Characteristics and Ferrite Formation Mechanism by Multiple-Cyclic Annealing in Quenching and Partitioning Steel
- Author
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Fei Peng, Yunbo Xu, and Xingli Gu
- Subjects
Quenching ,Austenite ,Materials science ,Carbon steel ,Annealing (metallurgy) ,Metals and Alloys ,engineering.material ,Lath ,Microstructure ,Industrial and Manufacturing Engineering ,Ferrite (iron) ,Martensite ,engineering ,Composite material - Abstract
Quenching and partitioning (Q&P) treatment is a novel method to produce advanced high strength steel with excellent mechanical properties. In this study, combination of multiple-cyclic annealing and Q&P process was compared with traditional cold-rolled Q&P steel to investigate the microstructural characteristics and austenite retention. The results showed that retained austenite in traditional Q&P sample was principally located in the exterior of austenite transformation products, while those in multiple-cyclic annealing samples were mainly distributed inside the transformation products. With the increase in cyclic annealing number, both of austenite fraction and austenite carbon content increased, attributing to higher initial austenite carbon content and larger number of austenite/neighbored phase interface to act as carbon partitioning channel. In traditional Q&P sample, the deformed ferrite was recrystallized by sub-grain coalescence, while the austenite was newly nucleated and grew up during annealing process. As a comparison, the ferrite in multiple-cycle annealing samples was formed by means of three routes: tempered martensite that completely recovered with retention of interior martensite variant, epitaxial ferrite that formed on basis of tempered martensite, ferrite that newly nucleated and grew up during the final annealing process. Both of lath martensite and twin martensite were formed as initial martensite and then tempered during partitioning process to precipitate e carbide with C enrichment, Mn enrichment and homogeneous Si distribution. Compared with the traditional cold-rolled Q&P steel, the Q&P specimens after multiple-cyclic annealing show smaller strength and much larger elongation, ascribing to the coarser microstructure and more efficient transformation induced plasticity (TRIP) effect deriving from retained austenite with high carbon content and larger volume fraction. The application of double annealing treatment can optimize the mechanical properties of Q&P steel to show a striking product of strength and elongation as about 29 GPa%, which efficiently exploit the potential of mechanical performance in low carbon steel.
- Published
- 2021
6. Effect of tempering and partitioning (T&P) treatment on microstructure and mechanical properties of a low-carbon low-alloy quenched and dynamically partitioned (Q-DP) steel
- Author
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Xiaodong Tan, Wenjun Lu, Ning Guo, Bo Song, Xi Rao, Yunbo Xu, and Shengfeng Guo
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2023
7. Single-cell Whole RNA Sequencing from Tumor-Infiltrating Lymphocyte
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Biaoru Li and Yunbo Xu
- Published
- 2022
8. A Thermodynamic Model for Pure and Binary Adsorption Equilibria of N2 and O2 on Lithium-Exchanged Low Silicon-to-Aluminum Ratio X Zeolite
- Author
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Yunbo Xu, Qilin Wu, Huicheng Yan, Zhi Wang, Yumeng Dang, Mingcheng Yu, Yagu Dang, Li Li, and Yiming Zi
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Air separation ,Silicon ,General Chemical Engineering ,chemistry.chemical_element ,Binary number ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Pressure swing adsorption ,Adsorption ,020401 chemical engineering ,chemistry ,Chemical engineering ,Aluminium ,Lithium ,0204 chemical engineering ,Zeolite - Abstract
To accurately describe the adsorption equilibria of N2 and O2 on LiLSX zeolite in the design of air separation by pressure swing adsorption, an applicable model (aNRTL–RAST) was developed. It was b...
- Published
- 2021
9. Composition and Morphology Modulation of Bimetallic Nitride Nanostructures on Nickel Foams for Efficient Oxygen Evolution Electrocatalysis
- Author
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Xiaokang Wan, Xianyun Wang, Dashun Lu, Yunbo Xu, Gezhong Liu, Yanming Fu, Taotao Shui, Haitao Wang, and Zude Cheng
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oxygen evolution ,nanocorals ,electrocatalysis ,bimetallic nitrides ,Physical and Theoretical Chemistry ,Catalysis ,General Environmental Science - Abstract
Metal-nitrides-based electrocatalysts for efficient oxygen-evolution have been extensively studied as one of the most promising candidates to fulfil the demand for future energy-conversion and storage. Herein, a series of NixCo1−xO- and NixCo1−xN-based nanostructures on nickel foams were reported to show excellent activities for oxygen-evolution reaction. The catalysts were prepared and modulated rationally via a facile-hydrothermal method, followed by high-temperature calcination under air or nitrogen atmosphere. The optimal bimetallic-nitride catalyst Ni0.3Co0.7N shows a small overpotential of 268 mV at 20 mA cm−2, and a Tafel slope of 66 mV dec−1 with good stability. The enhanced OER-performance is ascribed to the synergetic effect of the unique morphology and the intrinsic catalytic property of the nanostructure after nitridation.
- Published
- 2023
10. Texture evolution in twin-roll strip cast non-oriented electrical steel with strong Cube and Goss texture
- Author
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Longzhi Zhao, Yanchuan Tang, Jiao Haitao, R.D.K. Misra, Mingjuan Zhao, Mingxue Shen, Yong Hu, Dejia Liu, and Yunbo Xu
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010302 applied physics ,Equiaxed crystals ,Materials science ,Polymers and Plastics ,Metals and Alloys ,Nucleation ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,0103 physical sciences ,Ceramics and Composites ,engineering ,Crystallite ,Composite material ,0210 nano-technology ,Shear band ,Electron backscatter diffraction ,Electrical steel - Abstract
Increasing magnetically favorable //ND texture components is a key challenge in the preparation of high-efficiency non-oriented electrical steels. In this study, an Fe-1.3 wt% Si steel with strong Cube ({100} ) and Goss ({110} ) texture was successfully produced by novel twin-roll strip casting, cold rolling and annealing process. The microstructure and texture of the material was characterized by optical microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). The origin and formation mechanism of texture are described from the perspective of deformation and recrystallization behavior of specifically oriented grains. It was observed that initial Cube rotated toward {013} -{110} besides rotation toward {001} -{001} during cold rolling. In addition, new Cube deformation bands were developed in the deformed {115} -{115} grains. Cube components were partly retained as large block, small band structure and crystallite after heavy cold rolling. The Cube deformation structures served as nucleation sites of new Cube grains. The shear band within {114} , {112} and {111} matrix also provided some Cube nuclei. Morphology change from near bar-shaped to equiaxed occurred during the growth of Cube and Goss grains. The formation of recrystallization texture is attributed to the oriented nucleation mechanism, and the orientation pinning and size effects that impacted the intensity of texture component. The low thickness of strip and coarse solidification microstructure with strong {100} texture are the decisive factors to obtain strong Cube and Goss texture in strip-cast non-oriented electrical steel.
- Published
- 2020
11. Improving Mn partitioning and mechanical properties through carbides-enhancing pre-annealing in Mn-reduced transformation-induced plasticity steel
- Author
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D. Han, Yunbo Xu, Fei Peng, Weihua Sun, Rendong Liu, and Zou Ying
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010302 applied physics ,Austenite ,Materials science ,Cementite ,Annealing (metallurgy) ,Intercritical annealing ,Mechanical Engineering ,Metallurgy ,Metals and Alloys ,02 engineering and technology ,Plasticity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Carbide ,Ferritic matrix ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,0103 physical sciences ,General Materials Science ,0210 nano-technology - Abstract
A novel processing strategy was proposed, first to promote Mn partitioning behavior during intercritical annealing, second to improve the fraction and stability of retained austenite (RA) and third to enhance mechanical properties of Mn-reduced transformation-induced plasticity (TRIP) steel. By deliberately preparing large-fractioned Mn-enriched cementite before final annealing, the intercritical austenite was encouraged to inherit relatively high Mn content from pre-existing cementite. Eventually, the formation of sufficiently stable RA together with the precipitation of fine VC particles in ferritic matrix contributes to much better yield strength-tensile strength-ductility combination of 763 MPa-1022 MPa-46.4%, which is superior to many steels containing higher Mn concentrations.
- Published
- 2020
12. Improving Mechanical Properties of Welds Through Tailoring Microstructure Characteristics and Fracture Mechanism in Multi-Pulse Resistance Spot Welding of Q&P980 Steel
- Author
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Yi Jing, Yunbo Xu, Dongxiao Wang, Lin Lu, Jiayu Li, and Yongmei Yu
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
13. A Novel Process for Hot-Galvanized Q&P Steel with Excellent Yield-Ductility Synergy by Prior Treatment
- Author
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Yu Wang, Tianyu Zhang, Yunbo Xu, Yuan Wang, Xiaoying Hou, and Weihua Sun
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History ,Polymers and Plastics ,Business and International Management ,Industrial and Manufacturing Engineering - Published
- 2022
14. Tracing the recrystallization of warm temper-rolled Fe–6.5 wt% Si non-oriented electrical steel using a quasi in situ EBSD technique
- Author
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Steve Yue, Youliang He, Jianping Li, Yunbo Xu, and Haijie Xu
- Subjects
Materials science ,Mechanical Engineering ,Metallurgy ,Nucleation ,Recrystallization (metallurgy) ,Magnetostriction ,engineering.material ,Microstructure ,Grain growth ,Mechanics of Materials ,engineering ,General Materials Science ,Crystallite ,Electrical steel ,Electron backscatter diffraction - Abstract
Fe–6.5 wt% Si non-oriented electrical steel is an excellent soft magnetic material due to the low core losses at high frequencies and near-zero magnetostriction. In this study, an Fe–6.5 wt% Si non-oriented electrical steel was processed by hot rolling, warm cross rolling, intermediate annealing, warm temper rolling and final annealing. The evolution of microstructure and microtexture during final annealing was investigated using a quasi in situ EBSD (electron backscatter diffraction) technique. After warm temper rolling, an area on the ND–RD (normal direction–rolling direction) cross section was marked by micro-hardness indents, and the recrystallization of individual grains in this area was traced under EBSD when the annealing time was increased. Due to the differences in the microstructure, texture and stored energy after warm temper rolling, the surface and center regions showed different recrystallization behaviors. The recrystallization of the surface region was essentially initiated by the growth of existing crystallites having lower stored energy than their neighboring areas (essentially no nucleation), while the center region showed both nucleation and grain growth during annealing. The growth rates of individual grains were evaluated with respect to the number of neighboring grains, and they approximately followed the von Neumann–Mullins law of grain growth. The surface region showed a much faster growth rate than the center region. The final texture was dominated by //ND and //ND in both the surface and center regions, due to the preferred growth of these grains.
- Published
- 2020
15. Two-stage warm cross rolling and its effect on the microstructure, texture and magnetic properties of an Fe-6.5 wt% Si non-oriented electrical steel
- Author
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Yunbo Xu, Jiao Haitao, Cheng Sifei, Jianping Li, Steve Yue, Youliang He, and Haijie Xu
- Subjects
Materials science ,Mechanical Engineering ,Recrystallization (metallurgy) ,Slip (materials science) ,engineering.material ,Magnetocrystalline anisotropy ,Microstructure ,Magnetic field ,Mechanics of Materials ,engineering ,General Materials Science ,Texture (crystalline) ,Deformation (engineering) ,Composite material ,Electrical steel - Abstract
Cross rolling is an effective processing technique used to optimize the crystallographic texture of electrical steel sheets. However, it is usually applied in cold rolling only. It is unknown how this rolling technique affects the microstructure and texture of electrical steels at elevated temperatures. In this study, a two-stage warm cross rolling scheme, i.e., rolling at elevated temperatures and in alternative directions with respect to the hot rolling direction (HRD), was applied to an Fe-6.5 wt% Si non-oriented electrical steel to produce thin steel sheets. The swapping of rolling direction between the two warm rolling stages significantly changed the deformation microstructure and texture, leading to different final recrystallization textures. These differences are attributed to the discrepancies in slip activities at elevated temperatures and to the different initial textures resulted from the change in rolling direction. The magnetic properties of the final steel sheets are evaluated by single sheet testing. Although the steel processed by warm rolling along HRD in the first stage and along HTD in the second stage exhibits a slightly higher magnetic flux density than other routes, it is shown that the magnetic flux density and core loss may have little relation to the crystallographic texture since the magnetocrystalline anisotropy caused by the texture is small.
- Published
- 2020
16. Joint investigation of strain partitioning and chemical partitioning in ferrite-containing TRIP-assisted steels
- Author
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Dierk Raabe, Yunbo Xu, Huansheng He, Di Wu, Dirk Ponge, Xiaodong Tan, Wenjun Lu, and Jun Yan
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010302 applied physics ,Austenite ,Quenching ,Digital image correlation ,Materials science ,Polymers and Plastics ,Bainite ,Metals and Alloys ,TRIP steel ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Strain partitioning ,Ferrite (iron) ,Martensite ,0103 physical sciences ,Ceramics and Composites ,Composite material ,0210 nano-technology - Abstract
We applied two types of hot-rolling direct quenching and partitioning (HDQ&P) schemes to a low-C low-Si Al-added steel and obtained two ferrite-containing TRIP-assisted steels with different hard matrix structures, viz, martensite or bainite. Using quasi in-situ tensile tests combined with high-resolution electron back-scattered diffraction (EBSD) and microscopic digital image correlation (µ-DIC) analysis, we quantitatively investigated the TRIP effect and strain partitioning in the two steels and explored the influence of the strain partitioning between the soft and hard matrix structures on the TRIP effect. We also performed an atomic-scale analysis of the carbon partitioning among the different phases using atom probe tomography (APT). The results show that the strain mainly localizes in the ferrite in both types of materials. For the steel with a martensitic hard-matrix, a strong strain contrast exists between ferrite and martensite, with the local strain difference reaching up to about 75% at a global strain of 12.5%. Strain localization bands initiated in the ferrite rarely cross the ferrite/martensite interfaces. The low local strain (2%–10%) in the martensite regions leads to a slight TRIP effect with a transformation ratio of the retained austenite of about 7.5%. However, for the steel with bainitic matrix, the ferrite and bainite undergo more homogeneous strain partitioning, with an average local strain in ferrite and bainite of 15% and 8%, respectively, at a global strain of 12.5%. The strain localization bands originating in the ferrite can cross the ferrite/bainite (F/B) interfaces and increase the local strain in the bainite regions, resulting in an efficient TRIP effect. In that case the transformation ratio of the retained austenite is about 41%. The lower hardness difference between the ferrite and bainite of about 178 HV, compared with that between the ferrite and martensite of about 256 HV, leads to a lower strain contrast at the ferrite/bainite interfaces, thus retarding interfacial fracture. Further microstructure design for TRIP effect optimization should particularly focus on adjusting the strength contrast among the matrix structures and tuning strain partitioning to enhance the local strain partitioning into the retained austenite.
- Published
- 2020
17. Improving the stretch flangeability of ultra-high strength TRIP-assisted steels by introducing banded structure
- Author
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Yuan Wang, Yunbo Xu, Xu Wang, Jiayun Zhang, Fei Peng, Xingli Gu, Yu Wang, and Wenzhu Zhao
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
18. Improving yield strength and elongation combination by tailoring austenite characteristics and deformation mechanism in medium Mn steel
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Jiayun Zhang, Yunbo Xu, Dingting Han, and Zelin Tong
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Mechanics of Materials ,Mechanical Engineering ,Metals and Alloys ,General Materials Science ,Condensed Matter Physics - Published
- 2022
19. Significance of epitaxial ferrite formation on phase transformation kinetics in quenching and partitioning steels: modeling and experiment
- Author
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Yunbo Xu, Xingli Gu, Fei Peng, and Dingting Han
- Subjects
Austenite ,Materials science ,Cooling rate ,Mechanics of Materials ,Bainite ,Mechanical Engineering ,Ferrite (iron) ,Martensite ,Solid mechanics ,Transformation kinetics ,Thermodynamics ,General Materials Science ,Epitaxy - Abstract
Experimental and simulation methods were applied to analyze the transformation kinetics of epitaxial ferrite (EF) formed during a continuous cooling process and relevant carbon content heterogeneity in a low-carbon quenching and partitioning steel, with an emphasis on the influence of austenite carbon heterogeneity issued from EF formation on subsequent martensite and bainite transformation behaviors. It revealed that EF transformation possessed a kinetic curve with sigmoid shape and accelerated with decreasing cooling rate. With EF/γ interface under negligible partition local equilibrium condition in Dictra simulation, the simulation EF transformation kinetics can reproduce the experimental results well and the partial inheritance of Mn and Si from austenite into EF was also predicted. Furthermore, martensite transformation behaviors (one-stage or two-stage transformation) significantly depended on cooling rate and were explained by the austenite carbon heterogeneity issued from EF formation. The increase in initial martensite fraction with elevating cooling rate accelerated the subsequent bainite transformation and was favorable to austenite retention as well.
- Published
- 2019
20. Influence of pre-tempering treatment on microstructure and mechanical properties in quenching and partitioning steels with ferrite-martensite start structure
- Author
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Yunbo Xu, D. Han, Jiayu Li, Xingli Gu, Fei Peng, and Xu Wang
- Subjects
010302 applied physics ,Austenite ,Materials science ,Cementite ,Annealing (metallurgy) ,Mechanical Engineering ,02 engineering and technology ,Work hardening ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Ferrite (iron) ,Martensite ,0103 physical sciences ,General Materials Science ,Tempering ,Composite material ,0210 nano-technology - Abstract
The low carbon micro-alloyed steel with start microstructure of ferrite-martensite was pre-tempered to be ferrite-tempered martensite microstructure before cold rolling. Then an identical quenching and partitioning process was applied to the cold rolled sheet with start microstructures of deformed ferrite-martensite (Q&P-UFC) and deformed ferrite-tempered martensite (Q&P-T). It revealed that the austenitization of Q&P-T was retarded and much more austenite with higher stability was obtained after annealing. In both cases, the austenite formed at recrystallized martensite boundaries was significantly fine, while that formed at recrystallized ferrite boundaries was much coarser. Although the retained austenite fraction (5–6%) and corresponding carbon content (1.1–1.2 wt.%) were identical in both cases, a significant Mn-enrichment of retained austenite was only observed in Q&P-T related to the pre-existed Mn-enriched cementite and hence the corresponding TRIP effect in Q&P-T occurred at relatively larger strain. Moreover, abundant martensite variant combination with twin boundary was observed and exhibited dispersive distribution in Q&P-T. The work hardening behaviors of both cases showed three-stage variation, successively ascribed to the dislocation glide of ferrite, TRIP effect of retained austenite and dislocation intersection/tangle of ferrite and martensite, respectively. Both samples exhibited excellent combination of strength and ductility with UTS larger than 1000 MPa and TEL larger than 20%, and Q&P-UFC was favorable to obtain high strength level, while Q&P-T possessed better ductility and excellent combination of strength and ductility.
- Published
- 2019
21. Role of martensite/austenite constituents in novel ultra-high strength TRIP-assisted steels subjected to non-isothermal annealing
- Author
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Yuan Wang, Fei Peng, Xingli Gu, R.D.K. Misra, and Yunbo Xu
- Subjects
010302 applied physics ,Austenite ,Materials science ,Bainite ,Annealing (metallurgy) ,Mechanical Engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Mechanics of Materials ,Martensite ,0103 physical sciences ,Ultimate tensile strength ,Volume fraction ,General Materials Science ,Composite material ,0210 nano-technology ,Austempering - Abstract
A novel ultra-high strength transformation-induced plasticity (TRIP) steels with submicron-size martensite/austenite (M/A) constituents was processed by non-isothermal annealing process and compared with quenching and partitioning (Q&P) steels. The microstructure was characterized by means of SEM equipped with EPMA, XRD, EBSD and TEM and its effects on tensile strength and ductility were studied. The non-isothermal annealing significantly refined the parent austenite grains and enhanced inhomogeneous distribution of C atoms within the grains. Moreover, a large fraction of M/A constituents were separated and refined to hundreds of nanometers through bainite transformation in TRIP steels, while blocky retained austenite mainly existed near the carbon-rich prior grain boundaries in Q&P steel. TRIP steels had a higher content of less stable retained austenite by isothermal bainite transformation than Q&P steel, thereby favoring for improving the ductility. The contribution of fresh martensite to the ultimate tensile strength increased gradually from 49.7% to 67.3% with increase in the volume fraction of fresh martensite in TRIP steels. Optimizing the volume fraction and size of M/A constituents was important to obtain a high ultimate strength with desired ductility. The excellent mechanical properties were obtained in TRIP-350 (austempering at 350 °C) with ultimate tensile strength of 1011 MPa, total elongation of 28.80% and the product of strength and elongation (PSE) of 29.1 GPa%, exceeded the properties of Q&P steel.
- Published
- 2019
22. Carbon and strain partitioning in a quenched and partitioned steel containing ferrite
- Author
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Dierk Raabe, Di Wu, Xiaodong Tan, Xiao-Long Yang, Dirk Ponge, Xi Rao, Yunbo Xu, and Wenjun Lu
- Subjects
010302 applied physics ,Austenite ,Quenching ,Materials science ,Polymers and Plastics ,Metals and Alloys ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Strain partitioning ,Martensite ,Ferrite (iron) ,0103 physical sciences ,Ceramics and Composites ,Composite material ,0210 nano-technology ,Electron backscatter diffraction ,Tensile testing - Abstract
We applied a hot rolling direct quenching and partitioning (HDQ&P) process to a low-C low-Si Al-added steel and obtained a Q&P steel containing 40 vol % of ferrite. Microstructure characterization was performed by means of SEM, EBSD, TEM and XRD. Atomic-scale characterization of carbon partitioning among the phases was carried out by atom probe tomography (APT). The carbon distribution in the retained austenite and near the martensite/retained austenite interfaces was quantitatively analyzed to study its partitioning behavior. The macroscopic strain distribution evolution across the tensile sample surface was investigated using macro digital image correlation (DIC) analysis. Combining these results with joint micro-DIC and EBSD analysis during quasi in-situ tensile testing, we investigated the strain partitioning among the different phases and the TRIP effect. Coupling of these results enabled us to reveal the relation among carbon partitioning, strain partitioning and the TRIP effect. The large blocky retained austenite with a side length of about 300–600 nm located near the ferrite/martensite (F/M) interfaces has low stability and transforms to martensite during the early deformation stages, i.e. at average strain below 21%. The retained austenite films in the centers of the martensite regions are more stable. The carbon distribution in both, the martensite and the retained austenite are inhomogeneous, with 0.5–2.0 at. % in the martensite and 4.0–7.5 at. % in the retained austenite. Strong carbon concentration gradients of up to 1.1 at. %/nm were observed near the martensite/retained austenite interfaces. The large blocky retained austenite (300–600 nm in side length) near the F/M interfaces has 1.5–2.0 at. % lower carbon content than that in the narrow retained austenite films (20–150 nm in thickness). The ferrite is soft and deforms prior to the martensite. The strain distribution in ferrite and martensite is inhomogeneous, varying by up to 20% within the same phase at an average strain of about 20%. Ferrite deformation is the main origin of ductility of the material. The balance between ferrite fraction and martensite morphology controls the TRIP effect and its efficiency in reaching a suited combination of strength and ductility. Reducing the ferrite volume fraction and softening the martensite by coarsening and polygonization can enhance the strain carried by the martensite, thus promoting more retained austenite in the martensite regions enabling a TRIP effect. The enhancement of the TRIP effect and the decrease of the strain contrast between ferrite and martensite jointly optimize the micromechanical deformation compatibility of the adjacent phases, thus improving the material's ductility.
- Published
- 2019
23. Significant effect of as-cast microstructure on texture evolution and magnetic properties of strip cast non-oriented silicon steel
- Author
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Yifeng Du, Jianping Li, Jiao Haitao, Haijie Xu, Yunbo Xu, Wenzheng Qiu, R.D.K. Misra, and Guodong Wang
- Subjects
010302 applied physics ,Materials science ,Polymers and Plastics ,Annealing (metallurgy) ,Mechanical Engineering ,Metals and Alloys ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Grain size ,Strip casting ,Grain growth ,Mechanics of Materials ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,engineering ,Composite material ,0210 nano-technology ,Electrical steel - Abstract
In this study, two types of as-cast microstructure produced by strip casting were cold rolled and annealed to investigate the effect of initial microstructure on the textural evolution and magnetic properties of non-oriented silicon steel. The results indicated that the cold-rolled sheets of coarse-grained strip with pronounced {100} components exhibited stronger λ fiber (〈100〉//ND) and weaker γ fiber (〈111〉//ND) texture as composed to the fine-grained strip with strong Goss ({110}〈001〉) texture. After annealing, the former was dominated by η fiber (〈001〉//RD) texture with a peak at {110}〈001〉 orientation, while the latter consisted of strong {111}〈112〉 and relatively weak {110}〈001〉 texture. In addition, a number of precipitates of size ∼30–150 nm restricted the grain growth during annealing, resulting in recrystallization of grain size of ∼46 μm in the coarse-grained specimen and ∼41 μm in the fine-grained specimen. Ultimately, higher magnetic induction (∼1.72 T) and lower core loss (∼4.04 W/kg) were obtained in the final annealed sheets of coarse-grained strip with strong {100} texture.
- Published
- 2018
24. Improving Yield Strength-Tensile Strength-Elongation Combination by Tailoring Austenite Characteristics and Deformation Mechanism in Ultra-High-Strength TWIP/TRIP Steel
- Author
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Jiayun Zhang, Yunbo Xu, Dingting Han, and Zelin Tong
- Subjects
History ,Polymers and Plastics ,Business and International Management ,Industrial and Manufacturing Engineering - Published
- 2021
25. Atomic layer deposition assisted surface passivation on bismuth vanadate photoanodes for enhanced solar water oxidation
- Author
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Xiaokang Wan, Xianyun Wang, Chao Hu, Yunbo Xu, Nai Rong, Yanming Fu, Haowei Hu, and Xiangjiu Guan
- Subjects
Photocurrent ,Materials science ,Passivation ,General Physics and Astronomy ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Amorphous solid ,chemistry.chemical_compound ,Atomic layer deposition ,Chemical engineering ,chemistry ,Bismuth vanadate ,Surface modification ,Deposition (law) ,Surface states - Abstract
Bismuth vanadate (BiVO4) is one of the most promising metal oxide semiconductors for photoelectrochemical (PEC) water oxidation. Much efforts have been dedicated on accelerating the sluggish surface water oxidation kinetics. In this study, plasma enhanced atomic layer deposition and subsequent removal of Al2O3 ultrathin overlayers on bismuth vanadate were implemented to achieve the successful passivation of surface states and significant enhancement of PEC performance. Al2O3 ultrathin overlayers were first coated on BiVO4 surface via plasma enhanced atomic layer deposition with various deposition cycles, which resulted in the decrease of PEC water oxidation activity due to the poor conductivity. The subsequent removal of surface amorphous Al2O3 passivated the surface states of the photoanodes and significantly enhanced the photocurrent densities. The passivated BiVO4 exhibited a photocurrent density of 1.34 mA·cm−2 at 1.23 V vs. RHE, which is 73% higher than that of unmodified BiVO4. This work provides a novel strategy and deep insights on surface modification of semiconductor for photoelectrochemical energy conversion.
- Published
- 2022
26. Versatile Polypropylene Copolymers from a Pilot-Scale Spheripol II Process
- Author
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Han Xiaoyu, Wenqian Kang, Jie Fan, Yunbo Xu, Renwei Xu, and Xiong Wang
- Subjects
Materials science ,Polymers and Plastics ,Spheripol process ,02 engineering and technology ,01 natural sciences ,Article ,lcsh:QD241-441 ,chemistry.chemical_compound ,polypropylene polymerization ,random PP (RPP) ,lcsh:Organic chemistry ,Natural rubber ,Phase (matter) ,Copolymer ,Composite material ,impact PP with high clarity ,Polypropylene ,chemistry.chemical_classification ,010405 organic chemistry ,Flexural modulus ,Comonomer ,Izod impact strength test ,General Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,visual_art ,visual_art.visual_art_medium ,0210 nano-technology ,impact PP - Abstract
Polypropylene (PP) is one of the most widely used polymers. In this paper, three types of PPs including random PP, impact PP, and impact PP with high clarity, were prepared through a 75 kg/h pilot-scale Spheripol II process. The three produced PPs were produced by the selection or combination the two loops and gas phase reactor and controlling the comonomer and hydrogen concentrations. The three prepared PPs then were pelleted with the clarified nucleating agent NX 8000 and tested for mechanical, thermal, and optical properties. Their molecular structures and rubber phase size were also investigated by GPC, 13C NMR, temperature rising elution fractionation (TREF), XRD, SEM analysis, etc. The results showed that the random PP (PP-1) and the impact PP with high clarity (PP-3) obtained excellent optical transparency with a haze of 12.5% and 13.5% due to their small rubber phase size (roughly &le, 100 nm), while the impact PP (PP-2) obtained bad transparency with a haze of 98.8% due to the large rubber phase size (about 1 &mu, m) caused by the poor thermal compatibility with the PP matrix. The rubber phase content and ethylene/propylene sequence distributions of the three PPs varied much and resulted in different impact strengths and stiffness properties. PP-2 had a high impact strength of 14.5 kJ/m2 due to the rubber phase generated in the gas phase reactor. Except for the optical transparency, PP-3 gained stiffness and toughness, with 914 MPa of flexural modulus and 25.1 kJ/m2 of impact strength due to the unique molecular structure of its rubber phase.
- Published
- 2020
27. Influence of hot deformation on texture and magnetic properties of strip cast non-oriented electrical steel
- Author
-
Zhang Yuanxiang, Jiao Haitao, Jiaxin Jiang, Cao Guangming, Haijie Xu, Wei Xiong, Jianping Li, Yunbo Xu, and Raja Devesh Kumar Misra
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Nucleation ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Grain size ,Electronic, Optical and Magnetic Materials ,Permeability (electromagnetism) ,0103 physical sciences ,engineering ,Composite material ,0210 nano-technology ,Anisotropy ,Electrical steel - Abstract
The present study focuses on improving the magnetic properties and decreasing the anisotropy in non-oriented electrical steel by optimizing {1 0 0} recrystallization texture. As-cast Fe-1.3%Si strip with {1 0 0} texture produced by strip casting was subjected to hot rolling in the ferrite region, cold rolling, and recrystallization annealing. Magnetic properties and texture evolution after different stages of processing were studied. Annealed sample without hot rolling exhibited pronounced Cube and Goss texture, which led to high permeability but induced a large difference (∼0.15 T) in magnetic induction B50 between the maximum at 0° and minimum at 45° to the rolling direction. The introduction of hot rolling with 17–40% reduction weakened the intensity of recrystallization texture and had small influence on the nature of texture and magnetic induction. However, relatively complete {1 0 0} recrystallization texture was developed in the sample with hot rolling of 55% reduction. On the other hand, the average grain size of annealed sheets gradually increased with the increased hot rolling reduction. As a result, the magnetic induction and the core loss was optimized together with the improvement of anisotropy. The development of recrystallization texture is discussed on the basis of the deformed microstructure and nucleation mechanism, while the magnetic properties are correlated to the magnetic quality of the texture.
- Published
- 2018
28. Microstructure characterization and mechanical behavior analysis in a high strength steel with different proportions of constituent phases
- Author
-
Yuan Wang, Fei Peng, Hua Zhan, Jianping Li, Yunbo Xu, and Xingli Gu
- Subjects
010302 applied physics ,Austenite ,Materials science ,Bainite ,Annealing (metallurgy) ,Mechanical Engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Isothermal process ,Mechanics of Materials ,Martensite ,0103 physical sciences ,Ultimate tensile strength ,General Materials Science ,Grain boundary ,Composite material ,0210 nano-technology - Abstract
A high strength steel with Nb-V-Ti addition was heat treated by a series of isothermal bainite holding (IBH) processes and quenching and partitioning (Q&P) processes with different intercritical annealing temperatures. The microstructure observation showed that some martensite was formed during quenching in IBH condition with annealing temperature above 850 °C, mainly ascribed to heterogeneous carbon content distribution in parent austenite with relatively large size. Meanwhile, film-like RA in martensite, relatively coarser lath-like RA in bainite and blocky RA located in grain boundaries or phase boundaries were observed in both IBH and Q&P treatments. Moreover, Q&P process was proved to be more beneficial to retain austenite than IBH process, while the ability of austenite retention was similar in IBH conditions. An excellent combination of strength and ductility was obtained in Q&P process annealed at 880 °C with tensile strength of 1126 MPa and total elongation of ~ 18%, attributing to TRIP effect mainly occurred in the latter part of strain and fine microstructure with homogeneous distribution.
- Published
- 2018
29. Kinetic models of multiple-stage martensite transformation and subsequent isothermal bainite formation excluding ε-carbide precipitation in intercritical quenching and partitioning steels
- Author
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Dingting Han, Yunbo Xu, Fei Peng, and Xingli Gu
- Subjects
Austenite ,Materials science ,Annealing (metallurgy) ,Cementite ,Bainite ,Mechanical Engineering ,Thermodynamics ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Isothermal process ,0104 chemical sciences ,Carbide ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Martensite ,Stress relaxation ,lcsh:TA401-492 ,General Materials Science ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology - Abstract
The kinetic models of multiple-stage martensite transformation and subsequent isothermal bainite formation were investigated in intercritical quenching and partitioning steels. The modified K-M model that considering instantaneous kinetic characteristics was established and can well describe the kinetics of respective stage of martensite transformation, which was explained as a synergistic result of transformation stress relaxation and austenite plastic accommodation. The selection and combination of martensite variants played a vital role in stress relaxation of stage-2 martensite transformation. The precipitation of ε carbide inside initial martensite was initiated during isothermal partitioning process, while cementite formation was entirely suppressed. Meanwhile, the ε carbide was confirmed to be significantly Mn-enriched, while no obvious difference in the distribution of Si element. Moreover, a modified model based on the dilatometric results excluding ε carbide precipitation was applied to describe isothermal bainite transformation kinetics and revealed that the autocatalytic effect is negligible in samples evaluated here. The accelerated effect of initial martensite on bainite transformation was ascribed to the pre-existed defect originated from martensite formation and was enhanced with the increase in initial martensite fraction. The bainite transformation kinetics with identical annealing condition and partitioning temperature evaluated here can be precisely predicted, irrespective of initial martensite fraction. Keywords: Quenching and partitioning steel, Multiple-stage martensite transformation, Isothermal bainite transformation, ε-Carbide, Kinetic model
- Published
- 2019
30. Aging characteristics and strengthening behavior of a low-carbon medium-Mn Cu-bearing steel
- Author
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Lingfei Cao, D. Han, Hui Song, S.Q. Chen, Zou Ying, Z.P. Hu, R.D.K. Misra, and Yunbo Xu
- Subjects
010302 applied physics ,Shearing (physics) ,Austenite ,Materials science ,Mechanical Engineering ,02 engineering and technology ,Atom probe ,Plasticity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,law.invention ,Precipitation hardening ,Mechanics of Materials ,law ,0103 physical sciences ,Volume fraction ,General Materials Science ,Composite material ,Elongation ,0210 nano-technology ,Ductility - Abstract
We describe here the aging characteristics and strengthening behavior of a low-carbon medium-Mn Cu precipitation-strengthened steel. Atom probe tomography (APT) was employed to characterize the evolution of Cu-rich precipitates in terms of mean radius, number density and volume fraction. Aging at 500 °C and 550 °C for 1 h resulted in substantial coherent body-centered cubic (bcc) Cu-rich precipitates with mean radius of 1.35 and 2.59 nm, respectively. The precipitation strengthening mechanism for these two aging conditions was shearing mechanism and the corresponding strengthening contribution was ~ 266 and ~ 312 MPa, respectively. Here, coherency strengthening and modulus strengthening played a major role, while the contribution of chemical strengthening was relatively small. With increased aging temperature to 600 °C, the precipitates grew and coarsened to elongated shape with incoherent face-centered cubic (fcc) structure, and the strengthening mechanism was Orowan mechanism with a contribution of ~ 232 MPa. Increasing the aging temperature also facilitated the formation of retained austenite, which was of great benefit to plasticity without pronounced deterioration on precipitation strengthening. Ultra-high yield strength of 1020 MPa with superior total elongation of 25.8% was obtained in the sample aged at 600 °C for 1 h. The excellent mechanical properties derived from the combination of precipitation strengthening by Cu-rich precipitates and plasticity effect of retained austenite can be considered as a design principle to simultaneously optimize strength and ductility.
- Published
- 2018
31. Influence of grain size and texture prior to warm rolling on microstructure, texture and magnetic properties of Fe-6.5 wt% Si steel
- Author
-
Jiao Haitao, Jianping Li, Yunbo Xu, S.F. Cheng, Haijie Xu, and R.D.K. Misra
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Nucleation ,Recrystallization (metallurgy) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Grain size ,Electronic, Optical and Magnetic Materials ,Grain growth ,0103 physical sciences ,Composite material ,0210 nano-technology - Abstract
Fe-6.5 wt% Si steel hot bands with different initial grain size and texture were obtained through different annealing treatment. These bands were then warm rolled and annealed. An analysis on the evolution of microstructure and texture, particularly the formation of recrystallization texture was studied. The results indicated that initial grain size and texture had a significant effect on texture evolution and magnetic properties. Large initial grains led to coarse deformed grains with dense and long shear bands after warm rolling. Such long shear bands resulted in growth advantage for {1 1 3} 〈3 6 1〉 oriented grains during recrystallization. On the other hand, sharp {11 h} 〈1, 2, 1/h〉 (α∗-fiber) texture in the coarse-grained sample led to dominant {1 1 2} 〈1 1 0〉 texture after warm rolling. Such {1 1 2} 〈1 1 0〉 deformed grains provided massive nucleation sites for {1 1 3} 〈3 6 1〉 oriented grains during subsequent recrystallization. These {1 1 3} 〈3 6 1〉 grains were confirmed to exhibit an advantage on grain growth compared to γ-fiber grains. As a result, significant {1 1 3} 〈3 6 1〉 texture was developed and unfavorable γ-fiber texture was inhibited in the final annealed sheet. Both these aspects led to superior magnetic properties in the sample with largest initial grain size. The magnetic induction B8 was 1.36 T and the high frequency core loss P10/400 was 17.07 W/kg.
- Published
- 2018
32. VORTEX GENERATORS IN A TUBE FOR THERMAL ENHANCEMENT
- Author
-
M. D. Islam and Yunbo Xu
- Subjects
Materials science ,Thermal ,Tube (fluid conveyance) ,Mechanics ,Vortex generator ,Atomic and Molecular Physics, and Optics - Published
- 2018
33. The relationships of microstructure-mechanical properties in quenching and partitioning (Q&P) steel accompanied with microalloyed carbide precipitation
- Author
-
Yuan Wang, Yunbo Xu, Fei Peng, Xunda Liu, Jianping Li, and Xingli Gu
- Subjects
Austenite ,Quenching ,Materials science ,Carbon steel ,Cementite ,Mechanical Engineering ,Metallurgy ,02 engineering and technology ,Lath ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,020501 mining & metallurgy ,Carbide ,chemistry.chemical_compound ,0205 materials engineering ,chemistry ,Mechanics of Materials ,Martensite ,Ferrite (iron) ,engineering ,General Materials Science ,0210 nano-technology - Abstract
A low carbon steel microalloyed with Nb-V-Ti were heat treated by means of two-step quenching and partitioning (Q&P) process after partial austenitization. Combined use of SEM equipped with EBSD, XRD and TEM showed that the microstructure was composed of intercritical polygonal ferrite, tempered lath martensite, secondary twin martensite and carbon-enriched retained austenite, as well as microalloyed carbides (mainly VC) precipitated inside ferrite and martensite. When increasing partitioning time from 0 s to 3600 s, the volume fraction of retained austenite increased up to 6.5% with mean carbon content in austenite keeping a constant level. The retained austenite kept K-S orientation relationship with adjacent tempered lath martensite and neighboring secondary twin martensite in different martensite packet. As partitioning time increased up to 3600 s, the initial lath martensite tempered gradually to ferrite without any cementite formation.
- Published
- 2018
34. Effect of rolling temperature on the microstructure, texture, and magnetic properties of strip-cast grain-oriented 3% Si steel
- Author
-
Cao Guangming, Yang Wang, R.D.K. Misra, Xiang Lu, Guodong Wang, Guo Yuan, Yunbo Xu, Feng Fang, Meng-Fei Lan, and Zhang Yuanxiang
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Mechanical Engineering ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,Homogeneous microstructure ,Microstructure ,01 natural sciences ,Mechanics of Materials ,0103 physical sciences ,Stored energy ,Solid mechanics ,engineering ,General Materials Science ,Composite material ,0210 nano-technology ,Electrical steel - Abstract
The effect of rolling temperature on the evolution of microstructure, texture, and magnetic properties of ultra-low-carbon grain-oriented silicon steel was studied in strip-casting process. Dynamic strain-aging (DSA) behavior was observed during warm rolling in the temperature range of ~ 200 to 400 °C based on the fact that majority of the inhibitor elements remained in solution during the strip-casting process. Considering the initial coarse grains with strong {100} fiber prior to rolling, the cold-rolled specimen exhibited pronounced α-fiber and weak γ-fiber texture. However, intense shear bands and high stored energy regardless of the orientation were obtained in the warm-rolled specimens at the DSA temperature, accompanied by weak α-fiber and strong γ-fiber texture. While homogenous microstructure with lower stored energy was observed in the case of high temperature, the differences in shear bands and stored energy governed by the rolling temperature were strongly related to the extent of DSA effect, which is attributed to distinct characteristic of rolling and recrystallization texture. After recrystallization annealing, fine-grained homogeneous microstructure with strong Goss and γ-fiber texture was obtained at the DSA temperature, while relatively random texture with much more α-fiber and θ-fiber components was observed in the case of high temperature. The microstructure and texture of primary annealed sheets exhibited sufficient Goss grains and favorable surrounding matrix with pronounced γ-fiber texture, which was responsible for the perfect secondary recrystallization annealing in the warm-rolled specimens at the DSA temperature. The present study suggests that texture optimization of strip-cast grain-oriented silicon steel can be achieved by warm rolling in the appropriate temperature range, with improved magnetic properties.
- Published
- 2018
35. Effect of intercritical rolling temperature on microstructure-mechanical property relationship in a medium Mn-TRIP steel containing δ ferrite
- Author
-
Z.P. Hu, Diwen Hou, Zou Ying, D. Han, Yunbo Xu, S.Q. Chen, and R.D.K. Misra
- Subjects
010302 applied physics ,Austenite ,Materials science ,Mechanical Engineering ,TRIP steel ,02 engineering and technology ,Lath ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Mechanics of Materials ,Martensite ,Ferrite (iron) ,0103 physical sciences ,Ultimate tensile strength ,engineering ,General Materials Science ,Composite material ,0210 nano-technology ,Grain boundary strengthening - Abstract
We elucidate the influence of intercritical rolling temperature on the microstructural evolution, mechanical properties and work-hardening behavior of a hot-rolled Fe-0.2C-6.5Mn-3Al-0.1V medium Mn transformation-induced-plasticity (TRIP) steel containing δ-ferrite. Tensile strength of 966 MPa, total elongation of 42.6% and yield strength of 705 MPa was obtained in the annealed steel subjected to a low intercritical rolling temperature. Rolling at a high intercritical rolling temperature promoted the partitioning of Mn from δ ferrite to prior austenite grains, and led to a martensitic matrix characterized by a fine lath structure. Subsequently, after intercritical annealing, the reversed austenite transformed from the martensitic matrix had high stability and small size. However, the reversed austenite with a high degree of Mn enrichment, fine lath structure and high stability provided a slow and less active TRIP effect. This was responsible for low work-hardening rate during deformation. In contrast, the high content of reversed austenite in the annealed steel subjected to low intercritical rolling temperature had relatively low stability and large lath width, exhibited serrated work-hardening behavior indicative of discontinuous TRIP effect. Additionally, the low intercritical rolling temperature led to a high density of dislocations in δ-ferrite, which effectively promoted VC precipitation after intercritical annealing, and enhanced yield strength. Furthermore, the formation of high angle boundary in δ-ferrite and the formation of pro-eutectoid ferrite at low intercritical rolling temperature also enhanced yield strength through grain boundary strengthening.
- Published
- 2018
36. Influence of coiling temperature on mechanical properties in hot rolling C-Mn-Si-Al steel
- Author
-
Xingli Gu, Yuan Wang, Yunbo Xu, Yongmei Yu, and Fei Peng
- Subjects
010302 applied physics ,Materials science ,Bainite ,Cementite ,02 engineering and technology ,Lath ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Industrial and Manufacturing Engineering ,chemistry.chemical_compound ,chemistry ,Artificial Intelligence ,Ferrite (iron) ,Martensite ,0103 physical sciences ,Ultimate tensile strength ,engineering ,Composite material ,Elongation ,0210 nano-technology - Abstract
A low carbon C-Mn-Si-Al steel was hot rolled with coiling temperatures ranged from 510 oC to 710 oC. The microstructure of specimens consisted of deformed ferrite, lath martensite, twin martensite and bainite. Cementite was only observed in sample coiled at 570 oC. With increasing coiling temperature, deformed ferrite fraction decreased and recrystallized ferrite fraction increased. The ultimate tensile strength increased gradually from 1084 MPa to 1183 MPa due to the increasing fraction of martensite and bainite. The optimal mechanical properties were obtained when coiled at 570 oC with an ultimate tensile strength of 1085 MPa and ultimate elongation of 19.1 %.
- Published
- 2018
37. High-permeability and thin-gauge non-oriented electrical steel through twin-roll strip casting
- Author
-
Li Chenggang, Jiao Haitao, Yunbo Xu, Wei Xiong, Raja Devesh Kumar Misra, Jian Niu, Zhang Yuanxiang, and Cao Guangming
- Subjects
010302 applied physics ,Materials science ,Mechanical Engineering ,Metallurgy ,Nucleation ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Strip casting ,Mechanics of Materials ,0103 physical sciences ,lcsh:TA401-492 ,engineering ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,Composite material ,0210 nano-technology ,Electrical steel - Abstract
Texture optimization has always been a challenge to fabricate non-oriented electrical steels (NOES). In the present study, thin-gauge NOES with high permeability was successfully processed using an innovative and convenient twin-roll strip casting process without hot rolling. The relation between the as-cast microstructure, processing route and texture evolution was studied. The results indicated that as-cast strip with coarse grains exhibited strong {100}〈0vw〉 texture and unique {110}〈110〉 component. Annealed sheets processed by one-stage rolling displayed pronounced {111}〈112〉, {223}〈110〉 components and weak Cube and Goss texture. Micro-texture characteristics revealed that {100}〈0vw〉 texture was partially retained from initial grains, and new Cube and Goss substructures were generated within {110}〈110〉 deformed grains during cold rolling. This was responsible for the development of Cube and Goss recrystallization texture. Furthermore, the application of two-stage rolling not only reinforced these two behavior, but also accelerated the nucleation of η grains because of the increased shear bands in cold-rolled sheets. In this manner, an improved texture consisting of dominant η-fiber, weak γ-fiber and optimized magnetic properties (B50 = 1.72 T, P10/400 = 14.91 W/kg) were obtained. Keywords: Thin-gauge non-oriented electrical steel, Twin-roll strip casting, Microstructure, Texture, Magnetic properties
- Published
- 2017
38. Insignificant influence of the matrix on the melting of ice confined in decorated mesoporous silica
- Author
-
Zhenyan Zhao, Lianwen Wang, and Yunbo Xu
- Subjects
Matrix (chemical analysis) ,Materials science ,02 engineering and technology ,Mesoporous silica ,Composite material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,0210 nano-technology ,Condensed Matter Physics ,01 natural sciences ,Critical examination ,0104 chemical sciences - Abstract
For a critical examination of matrix effect on the melting of confined ice, mesoporous silica (SBA-15) are synthesised and decorated with n-Alkyl and aminopropyl groups to tune the surface hydropho...
- Published
- 2017
39. Effect of Rapid Heating on a Cold-Rolled Mn–Al Transformation-Induced Plasticity Steel with Coarse Delta-Ferrite
- Author
-
Xiao-Dong Tan, Peng Fei, Shi-Chuan Yu, Yunbo Xu, Hu Zhiping, Zou Ying, and Gu Xingli
- Subjects
010302 applied physics ,Delta ,Materials science ,Ferrite (iron) ,0103 physical sciences ,Metallurgy ,General Materials Science ,02 engineering and technology ,Plasticity ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences - Published
- 2017
40. High strength-toughness combination of a low-carbon medium-manganese steel plate with laminated microstructure and retained austenite
- Author
-
D. Han, Yunbo Xu, Z.P. Hu, G.Z. Wang, S.Q. Chen, Zou Ying, and R.D.K. Misra
- Subjects
010302 applied physics ,Austenite ,Toughness ,Materials science ,Mechanical Engineering ,Metallurgy ,Fracture mechanics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Mechanics of Materials ,Ferrite (iron) ,Martensite ,0103 physical sciences ,Ultimate tensile strength ,General Materials Science ,Composite material ,0210 nano-technology ,Stress concentration - Abstract
Three different grain structures of low-carbon medium-manganese steel were prepared through appropriate controlled rolling process. The laminated microstructure with a strong //rolling direction (RD) fiber texture was characterized by ultra-fine elongated ferrite, retained austenite and martensite phase arranged alternately along the RD. The steel with equiaxed grain structure exhibited a relatively low tensile strength of 960 MPa and an extremely poor low-temperature toughness of ~ 8 J at −196 °C. An enhanced upper shelf energy (> 450 J) and low-temperature toughness (~ 105 J at −196 °C), as well as an improved tensile strength (1145 MPa) was obtained in the steel with laminated microstructure. The laminated microstructure enabled the steel to be significantly stronger and tougher along the RD, which contributed to the high tensile strength to some extent. It is concluded that the combined effect of the ultra-fine elongated laminated microstructure, the possible interface decohesion and the existence of numerous {001} cleavage planes resulted in the occurrence of delamination. The delamination fracture enhanced the upper shelf energy mainly by promoting crack branching along the RD and thus suppressing crack propagation along the v-notch direction, which finally resulted in greater plastic deformation and significant increase in absorbed energy. Besides delamination toughening, transformation-induced plasticity (TRIP) effect of metastable retained austenite is believed to be responsible for the high cryogenic toughness, which can release stress concentration of crack tips and thus blunting cracks propagation.
- Published
- 2017
41. The impact of niobium on the microstructure, texture and magnetic properties of strip-cast grain oriented silicon steel
- Author
-
Yunbo Xu, Feng Fang, Guodong Wang, Cao Guangming, Xiang Lu, M.F. Lan, Guo Yuan, Yin-Ping Wang, Raja Devesh Kumar Misra, and Zhang Yuanxiang
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Precipitation (chemistry) ,Niobium ,chemistry.chemical_element ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Grain size ,Electronic, Optical and Magnetic Materials ,chemistry ,0103 physical sciences ,engineering ,Grain boundary ,Composite material ,0210 nano-technology ,Electrical steel - Abstract
We elucidate here the impact of niobium in ultra-low carbon grain oriented electrical steel (GOES) in terms of microstructure, texture, precipitation and magnetic properties that was processed by twin roll strip casting. Coarse and complex MnS + NbN precipitates, and fine NbN were nucleated at the grain boundaries and in the interior of the grain in the as-cast strip, which contributed to a small degree of grain refinement together with relatively random texture, and AlN precipitation was suppressed during the strip casting process. NbN continuously precipitated during the entire process and exhibited high stability during the reheating cycle, which provided stronger inhibiting force in comparison to AlN precipitates. As a consequence, fine and homogeneous inhibitors were obtained in the primary annealed sheet in the presence of Nb under cold rolling and annealing parameters used in the present study. On considering the effect of NbN particles or Nb in solution on the deformation and recrystallization behavior, the primary annealed Nb-containing sheet exhibited significantly more homogeneous microstructure in relation to Nb-free GOES, with grain size in the range of ∼8–12 μm, and was characterized by relatively more pronounced γ-fiber and weak Goss texture, beneficial for the abnormal growth of Goss grains. Furthermore, Nb-containing GOES experienced complete abnormal growth during secondary recrystallization annealing, such that the enhanced magnetic induction (B 8 as high as 1.88 T) was obtained. In summary, the present study underscores that NbN can be used as an effective inhibitor in ultra-low carbon grain oriented electrical steel using strip casting technology.
- Published
- 2017
42. Effect of Strip Casting on Magnetic Anisotropy of Non-Oriented Electrical Steels
- Author
-
Jiao Haitao, Xiang Lu, Guodong Wang, Yang Wang, Feng Fang, Cao Guangming, Li Chenggang, Yunbo Xu, and Zhang Yuanxiang
- Subjects
010302 applied physics ,Magnetic anisotropy ,Strip casting ,Materials science ,0103 physical sciences ,General Materials Science ,02 engineering and technology ,Composite material ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences - Published
- 2017
43. Tailoring austenite stability and mechanical behaviors of IQ&P steel via prior bainite formation
- Author
-
Yunbo Xu, Xingli Gu, and Fei Peng
- Subjects
010302 applied physics ,Austenite ,Materials science ,Bainite ,Mechanical Engineering ,chemistry.chemical_element ,02 engineering and technology ,Lath ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Isothermal process ,chemistry ,Mechanics of Materials ,Martensite ,0103 physical sciences ,engineering ,General Materials Science ,Composite material ,0210 nano-technology ,Ductility ,Carbon - Abstract
The prior carbide-free bainite (CFB) was introduced into a low carbon IQ&P steel via an isothermal bainitic holding (IBH) process, named as IBQ&P steel. It is essential to investigate the influence of prior CFB formation on microstructural evolution and mechanical properties, especially focused on austenite stability and mechanical behaviors. It reveals that the influence of prior CFB on austenite stability changed from deteriorated effect into mechanical stabilization with increasing IBH time, whilst the location of prior CFB expanded from the region adjacent to interface of constituent phases into the interior of parent austenite. Meanwhile, the amount of bainite with morphology of lath and blocky significantly increased accompanied by improvement of microstructural refinement, while the fraction of initial martensite with lath or twin structure decreased with existence of abundant tempered dislocation and e-carbide. As compared to IQ&P steel, the carbon content of retained austenite in IBQ&P steel was improved with elevated stability, ascribing to the retention of high carbon austenite in the exterior of parent austenite and refinement of microstructure. The practical carbon content of retained austenite was much larger than the predicted results merely considering carbon partitioning, while nearly close to that of NPLE/PLE transition line of γ to α transformation including synergistic partitioning of C, Mn and Si elements. Moreover, the high carbon retained austenite in IBQ&P steel gave rise to TRIP effect occurred at large strain with expanded range. Finally, the introduction of prior CFB significantly improved the combination of strength and ductility with optimal PSE value exceeding 30 GPa%, which was obtained by properly tailoring the decomposition and retention of metastable austenite.
- Published
- 2021
44. Effects of quenching temperature on bainite transformation, retained austenite and mechanical properties of hot-galvanized Q&P steel
- Author
-
Xiaoying Hou, Jiayu Li, Yunbo Xu, Tianyu Zhang, Yu Wang, and Weihua Sun
- Subjects
010302 applied physics ,Quenching ,Austenite ,Materials science ,Bainite ,Mechanical Engineering ,02 engineering and technology ,Lath ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Mechanics of Materials ,Ferrite (iron) ,Martensite ,0103 physical sciences ,engineering ,General Materials Science ,Dilatometer ,Composite material ,0210 nano-technology - Abstract
Over the last decade, demand has increased for developing the hot-galvanized quenching and partitioning (Q&P) steel to overcome the disadvantages associated with vehicle safety, fuel consumption and corrosion resistant. The present work aims to elucidate the effects of quenching temperature on phase transformation kinetics, microstructure evolutions and mechanical properties of a hot-galvanized Q&P steel (0.225C-0.85Si-2.02Mn-0.91Al, in wt.%) by combining modeling and experimental research. Using dilatometry, SEM, EBSD, EPMA, TEM, PED, XRD and Image-Pro Plus (IPP) software, we quantitatively investigated the microstructure evolution at different quenching temperatures. Results indicated that a larger fraction of primary martensite at lower quenching temperature could strongly promote subsequent bainite transformation kinetics, which is attributed to more martensite-austenite interfaces and defect density. By fitting the dilatometer curves and establishing the equation of transformation rate vs. quenching temperature, a Kolmogorov-Johnson-Mehl-Avram (KJMA) equation was established to describe insufficient bainite formation kinetics during high-temperature short-time overaging. Furthermore, a modified CCE model taking into account intercritical ferrite and short-time bainite transformation was proposed and the predicted RA fractions are more consistent with the experimental values. As the quenching temperature decreases, small-sized blocky RA along martensite boundaries and filmy RA between martensite laths increase, while coarse lath/blocky RA inside bainite structures or at bainite boundaries decreases gradually. In addition, the YS decreases from 763 MPa to 431 MPa with the increase of quenching temperature, while the UTS varies in a narrow range between 967 MPa and 1036 MPa. A stable TEL of 22.6–25.7% can be obtained at a wide range quenching temperature (150–275 °C), which is attributed to the joint effects of TRIP effect and multiphase structure. This research would be of guiding significance for the industrial practice.
- Published
- 2021
45. Relationship between crystallographic orientation, microstructure characteristic and mechanical properties in cold-rolled 3.5Mn TRIP steel
- Author
-
Weihua Sun, D. Han, Yunbo Xu, Jiayun Zhang, and Fei Peng
- Subjects
010302 applied physics ,Austenite ,Materials science ,Annealing (metallurgy) ,Cementite ,Mechanical Engineering ,TRIP steel ,Recrystallization (metallurgy) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Crystallography ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Ferrite (iron) ,0103 physical sciences ,General Materials Science ,0210 nano-technology ,Electron backscatter diffraction - Abstract
The relationship between crystallographic orientation, microstructure characteristic and mechanical properties in 3.5Mn transformation induced plasticity (TRIP) steel that subjected to different cold rolling reduction and annealing time was elucidated. Before the hot-rolled plates were cold rolled to different thicknesses, large-fractioned Mn-enriched cementite particles dispersed in ferrite matrix were deliberately prepared to enhance Mn-partitioning and improve austenite stability. The evolution of microstructure was performed by electron probe micro-analyzer (EPMA), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the mechanical properties of the intercritical annealed samples were evaluated by uniaxial tensile test at room temperature. The results show that the cementite dissolution, ferrite recrystallization and austenite formation are strongly coupled and interdependent, resulting in a complex ultra-fine microstructure composed of retained austenite, ferrite and cementite in the intercritical annealed samples. Moreover, the Schmid factor (SF) distribution within the range of 0.25–0.5 was studied to understand its correlation with the crystallographic orientation and mechanical property of the test steel. It is concluded that the mechanical properties of 3.5Mn TRIP steel can be improved when the annealing period, orientation and austenite stability are optimized.
- Published
- 2021
46. Effects of initial microstructure before cold rolling on microstructure evolution and mechanical behaviour of CGLcompatible Q&P steel
- Author
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Yunbo Xu, Yu Wang, and Tianyu Zhang
- Subjects
Materials science ,Composite material ,Microstructure - Abstract
Quenching and partitioning (Q&P) steels offer impressive combination of strength and ductility that can reduce the mass and improve the crash worthiness. In order to be able to meet consumer’s durability expectations, corrosion protection and galvanizability become crucial. In this paper, based on a cold-rolled high strength steel (0.225C-0.85Si-2.02Mn-0.91Al, in wt.%) and continuous galvanizing line (CGL) compatible Q&P treatment, the effects of the initial microstructure before cold-rolling were systematically investigated by means of SEM, EPMA, TEM, EBSD and XRD. It is shown that the resulting microstructure and mechanical properties after Q&P treatment are influenced by the initial microstructure. About 10.2-16.1vol.% RA are obtained, which is potential to gain the desired mechanical stability. Compared with “Q&P sample with initial microstructure prepared by quenching and austempering (i.e., Q&P(QAT))”, “Q&P sample with initial microstructure prepared by quenching and austempering followed by tempering (i.e., Q&P(QAT&T))” obtained a higher fraction of retained austenite (16.1%RA) and relatively low carbon content, thus resulted in an excellent ductility because of better mechanical stability and consequently more effective and sustained TRIP effect at high strain. With increasing the tempering time, the tempering degree of martensite increases markedly, while it does not have strong effects on the microstructures, leading to the similar fractions of RA and properties in “Q&P sample with initial microstructure prepared by quenching and tempering for 4min (i.e., Q&P(Q&T-1))” and “Q&P sample with initial microstructure prepared by quenching and tempering for 10min (i.e., Q&P(Q&T-2))”.
- Published
- 2021
47. A quasi in-situ EBSD study of the nucleation and growth of Goss grains during primary and secondary recrystallization of a strip-cast Fe-6.5 wt% Si alloy
- Author
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Yunbo Xu, Jiao Haitao, Jianping Li, Haijie Xu, Youliang He, and Steve Yue
- Subjects
In situ ,Materials science ,Mechanical Engineering ,Metallurgy ,Alloy ,Metals and Alloys ,Nucleation ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Grain growth ,Mechanics of Materials ,Materials Chemistry ,engineering ,Grain boundary ,0210 nano-technology ,Electron backscatter diffraction - Abstract
The nucleation and growth of Goss grains during primary and secondary recrystallization of a strip-cast grain-oriented Fe-6.5 wt% Si alloy were investigated using a quasi in-situ electron backscatter diffraction (EBSD) technique. During primary recrystallization at 700 °C, the Goss was found to nucleate from two locations in the deformed //ND (normal direction) grains: in the shear bands and at the grain boundaries. However, only those nucleated from the shear bands tended to survive during the subsequent grain growth. Even the survived Goss grains would not develop as abnormal Goss grains during secondary recrystallization. Abnormally growing Goss grains were formed at the surfaces when the primary recrystallization temperature was 850 °C, which grew into the center and consumed the entire thickness during secondary recrystallization. The abnormal growth of the Goss grains was attributed to the large fraction of 20–45° grain boundaries at the growing front, which essentially did not change during secondary recrystallization. Using a classical grain growth model, the migration velocities of Goss grains during abnormal growth were calculated, which were compared to the experimental migration velocities obtained from the quasi in-situ EBSD data. It was shown that the model could roughly predict the abnormal growth of the Goss grains during secondary recrystallization.
- Published
- 2021
48. Different coating on electrospun nanofiber via layer-by-layer self-assembly for their photocatalytic activities
- Author
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Cheng Wang, Tiexin Cheng, Zhaoyi Wang, Enyi Gong, Guangdong Zhou, Chunhong Sui, and Yunbo Xu
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Polyethylenimine ,Materials science ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Silver nanoparticle ,Electrospinning ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Chemical engineering ,Nanofiber ,Photocatalysis ,Surface charge ,Phosphotungstic acid ,0210 nano-technology ,Hybrid material - Abstract
The water-stable PAA/PVA/PW 12 nanofiber was firstly prepared by electrospinning and thermal treatments. The negatively charged phosphotungstic acid (PW 12 ), positively charged polyethylenimine (PEI) and silver nanoparticle (Ag NPs) were alternatively deposited onto the fibrous substrate by layer-by-layer (LBL) self-assembly technique. The photocatalytic activity of different coated LBL film was observed under visible light irradiation. The results indicated that the conversion rate of methylene blue (MB) was gradually decreased with increasing the number of bilayers pairs. The behavior might ascribe to the more polycation electrolyte PEI that prevented from permeating for the MB molecule. On the other hand, in terms of the effects of surface charges on the photocatalytic activity, negatively charged surface (PEI) n (PW 12 ) n indicated higher photocatalytic activity than that of positively charged surface (PEI) n (PW 12 ) n − 1 . For the Ag NPs deposited on the LBL film, Ag-(PEI) n (PW 12 ) n film were found to be a better photocatalytic activity than other multilayer films, specially, Ag-(PEI) 2 (PW 12 ) 2 exhibited the most excellent activity due to the influence of the synergy in the hybrid materials.
- Published
- 2017
49. Correlation between deformation behavior and austenite characteristics in a Mn-Al type TRIP steel
- Author
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D. Han, Zou Ying, Yunbo Xu, S.Q. Chen, Z.P. Hu, and R.D.K. Misra
- Subjects
Austenite ,Materials science ,Annealing (metallurgy) ,020502 materials ,Mechanical Engineering ,Metallurgy ,TRIP steel ,02 engineering and technology ,Work hardening ,Plasticity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Grain size ,0205 materials engineering ,Mechanics of Materials ,Ultimate tensile strength ,General Materials Science ,0210 nano-technology - Abstract
We investigate here the correlation between deformation behavior and retained austenite characteristics in a medium-Mn transformation-induced plasticity (TRIP) steel. The sample was characterized by a dual-phase microstructure consisting of ultra-fine grained ferrite and retained austenite with relatively high mechanical stability after annealing at 700 °C for 5 h. Both lath-like and blocky (granular) retained austenite with volume fraction of 38.7% and relatively inhomogeneous grain size was obtained. The tensile specimen exhibited outstanding mechanical properties with yield strength of 745 MPa, tensile strength of 1005 MPa and total elongation of 46%, as well as a distinctive work hardening behavior. The in-depth investigation on deformation behavior demonstrated that the transformation mechanism of retained austenite during deformation was strain-induced and the yielding behavior was controlled mainly by the deformation of soft ferrite phase. As to the multi-peak work hardening behavior, it is believed to be attributed to the inhomogeneous and discontinuous occurrence of TRIP effect, which resulted from the inhomogeneous stability of retained austenite. Moreover, the orientation of retained austenite (Schmid factors) was proved an important factor in determining the mechanical stability of retained austenite upon deformation, in addition to the heterogeneity of grain size. These two factors together resulted in the inhomogeneous stability of retained austenite.
- Published
- 2017
50. Evolution of microstructure and texture in grain-oriented 6.5%Si steel processed by strip-casting
- Author
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Cao Guangming, Yunbo Xu, R.D.K. Misra, Yandong Wang, Feng Fang, Guo Yuan, Xiang Lu, Wang Guanqi, and Zhang Yuanxiang
- Subjects
010302 applied physics ,Equiaxed crystals ,Materials science ,Fine grain ,Annealing (metallurgy) ,Mechanical Engineering ,Metallurgy ,02 engineering and technology ,Abnormal grain growth ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Superheating ,Strip casting ,Grain growth ,Mechanics of Materials ,0103 physical sciences ,General Materials Science ,0210 nano-technology - Abstract
Grain-oriented 6.5%Si steel was produced by strip-casting, followed hot rolling, cold rolling, primary annealing and secondary annealing. Microstructural and textural evolution was studied with particular focus on the effect of solidified microstructure on the ultimate microstructure and texture. The study indicated that solidified microstructure of the as-cast strip was determined by melt superheat. The relatively low melt superheat resulted in fine equiaxed grains with random texture, whereas large melt superheat led to coarse grains with moderate λ-fiber texture. After cold rolling, the fine-grained steel showed narrow pancake grain structure in comparison to the coarse-grained steel, which was similar to the microstructure of the initial as-cast strip. After primary annealing, fine equiaxed microstructure with favorable {111}⟨112⟩ texture was obtained in the fine-grained steel. While inhomogeneous microstructure with strong α-fiber and moderate γ-fiber texture was obtained in the coarse-grained steel. The desirable microstructure and texture in the fine-grained steel led to abnormal grain growth with B8 = 1.65 T after secondary annealing. By comparison, normal grain growth occurred in the coarse-grained sample with B8 = 1.37 T. Another observation was high frequency core losses of grain-oriented 6.5%Si steel sheet with adequate secondary grains was significantly lower than non-oriented 6.5%Si steel and grain-oriented 3.0%Si steel. The study suggests that the strip-casting is a suitable route to fabricate grain-oriented 6.5%Si steel, and the initial fine grain size with random texture is preferred to obtain adequate abnormal grain growth.
- Published
- 2017
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