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Activation Energy for Superplastic Flow Above Critical Temperature of Die Steels

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Journal of Iron and Steel Research International 2006年第5期13卷 4-6页

作者： wen jiu-ba ZHANG Ke-ke CHEN Fu-xiao YANG Yong-shun School of Materials Science and Engineering Henan University of Science and Technology Luoyang 471003 Henan China

Some commercial cold working die steels C.,Cr15 and CrWMn with ultra fine grain size were chosen as tested materials to research the activation energy for superplastic flow at different temperatures and strain rates above critical temperature. based on the Arrhenius equation, the activation energy for superplastic flow is evaluated. The activation energy at constant strain rate is estimated by the logσ, vs 1/T relationship. The results show that the ac tivation energy is usually small under the conditions of optimal flow. The characteristics of superplastic deformation of steels above the critical temperature were also analyzed.

关键词： superplasticity superplastic working activation energy

Optimization of spray conditions in cold spraying based on numerical analysis of particle velocity

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中国有色金属学会会刊：英文版 2004年第Z1期14卷 43-48页

作者： LI wen-ya LI Chang-jiu State Key Laboratory for Mechanical Behavior of Materials Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of MaterialsXi''an Jiaotong University Xi''an 710049 China

The effects of the parameters involved in cold spray on the acceleration of particles are systematically investigated by a CFD code in order to reveal the main factors influencing significantly particle velocity. The parameters involved include nozzle geometry parameters, processing parameters and properties of spray particles. It is found that driving gas type, operating pressure and temperature are main processing parameters which influence particle velocity. As for nozzle geometry, the expansion ratio and divergent section length of spray gun nozzle show significant effects. Moreover, the density, size and morphology of powder also have significant effects on particle velocity. The effects of those main parameters are summarized in a comprehensive equation obtained through nonlinear regression of the simulated results for the estimation of particle velocity. The interactions of the parameters on particle acceleration can be examined through the equation. Moreover, the optimization of the dimensions of spray gun nozzle and spray parameters can be realized based on the obtained results.

关键词： cold spraying numerical modeling particle acceleration impact velocity

Microstructure evolution of cold-sprayed coating during deposition and through post-spraying heat treatment

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中国有色金属学会会刊：英文版 2004年第Z1期14卷 49-54页

作者： LI Chang-jiu LI wen-ya State Key Laboratory for Mechanical Behavior of Materials Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of Materials Xi''an Jiaotong University Xi''an 710049 China

The microstructural features of cold-sprayed coatings were investigated using Cu, Ti and Zn feedstocks by optical microscopy, scanning electron microscopy and transmission electron microscopy to reveal the microstructure evolution mechanisms in cold spray. Four typical effects including tamping, refinement, impact-induced fusion and annealing were examined on microstrueture. It is found that the microstructure of cold spray coating is remarkably influenced by spray materials. Ti coatings consist of evident porous layer and Cu coatings present a limited porous layer only near the surface. It is clear that the successive tamping effect and dynamic refinement of grains significantly influence the microstructure evolution of cold-sprayed coating. The tamping effect leads to the densification of porous coating layer gradually and the refinement effect leads to the formation of fine microstructure. It is considered that the large difference in the formation of porous layer is attributed to the dynamic impact pressure and hardenability of materials. It is also found that the impact-induced fusion during deposition of Zn coating can also modify the interfacial microstructure between particles in cold spray coating. Moreover, the nanocrystalline phase can be formed at the interfaces among particles resulting from the localized melting of the interfaces and tamping effect. Furthermore, the annealing treatment can modify the microstructure and property of a cold-sprayed coating.

关键词： cold spraying coating microstructure evolution annealing treatment

Effect of Rare Earth on Void band of Diffusion Layer and Properties of Aluminized Steel

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Journal of Iron and Steel Research International 2006年第5期13卷 60-64,78页

作者： ZHANG Wei FAN Zhi-kang HU Peng-fei LONG Yong-qiang LIU Hua wen jiu-ba School of Materials Science and Engineering Xi＇an University of Technology Xi＇an 710048 Shaanxi China Department of Materials Engineering Luoyang College of Technology Luoyang 471003 Henan China School of Materials Science and Engineering Henan University of Science and Technology Luoyang 471003 Henan China

The effects of the addition of rare earth （RE） elements on the void band in the diffusion layer, and the re sistances to both oxidation and spalling of aluminized steel were investigated through high temperature oxidation and spalling tests. The results showed that RE had significant effects on the void band in the diffusion layer and the properties of aluminized steel. After diffusion treatment, a considerable number of the voids between the middle layer and transitional layer of pure aluminized coating, aggregated into wavy-line-shaped void bands parallel to the outer surface. For the RE added aluminized coating, only a few voids aggregated into intermittent block shapes. During high temperature oxidation at 800 ℃ for 200 h, the wavy void band of pure aluminized coating aggregated further into a linear crack parallel to the outer surface, and the internal oxidation occurred within them; the open cracks perpendicular to the surface penetrated through the diffusion layer. For the RE added aluminized coating, only a few voids aggregated into intermittent meniscus shapes. During cyclic spalling tests, the peeling, spallation, and pulver ulent cracking occurred along the void band in the diffusion layer of pure aluminized coating, but only a little spallation occurred in the diffusion layer of the RE-added aluminized coating, in which cracks perpendicular to the surface were much smaller than those of pure aluminized coating and did not penetrate through the diffusion layer. It is evident that RE addition can restrain the formation and aggregation of voids and subsequently improve the resistances to oxidation and spalling. The mechanism of the RE effect on the void band in the diffusion layer is also discussed.

关键词： rare earth void band crack internal oxidation oxidation resistance spalling resistance aluminized steel

A generalization of banach's lemma and its applications to perturbations of bounded linear operators

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Applied Mathematics(A Journal of Chinese Universities) 2024年第2期39卷 363-369页

作者： WANG Zi DING jiu WANG Yu-wen School of Mathematics Sciences Harbin Normal UniversityHarbin 150025China School of Mathematics and Natural Sciences The University of Southern MississippiHattiesburg MS 39406-5043USA Academic Committee Harbin Institute of PetroleumHarbin 150027China

Let X be a banach space and let P:X→X be a bounded linear *** an algebraic inequality on the spectrum of P,we give a new sufficient condition that guarantees the existence of(I-P)^(-1) as a bounded linear operator on X,and a bound on its spectral radius is also *** generalizes the classic banach *** apply the result to the perturbation analysis of general bounded linear operators on X with commutative perturbations.

关键词： banach lemma spectral radius generalized inverse perturbation analysis

Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field

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International Journal of Minerals,Metallurgy and Materials 2014年第7期21卷 696-701页

作者： Xin Su Guang-ming Xu jiu-wen Jiang Key Laboratory of Ministry of Education for Electromagnetic Processing of Materials Northeastern University Foshan Scien Aluminum Co. Ltd.

The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675℃ were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to theα-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.

关键词： aluminum alloys magnetic field roll-casting mechanical properties

Dual-function terahertz metasurface based on vanadium dioxide and graphene

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Chinese Physics B 2022年第9期31卷 286-292页

作者： jiu-Sheng Li Zhe-wen Li Centre for THz Research China Jiliang UniversityHangzhou 310018China

A dual-function terahertz metasurface based on VO_(2) and graphene is proposed in this *** consists of a gold layer embedded with VO_(2) patches,a SiO_(2) spacer layer,a VO_(2) layer,graphene and a SiO_(2) spacer *** the bottom VO2 layer is in the metallic state,the designed metasurface can achieve *** the top VO_(2) patches are in the metallic state,the proposed metasurface can be used as a single-band absorber with terahertz absorptance of 99.7% at 0.736 *** the top VO2 patches are in the insulating state,the designed structure behaves as a dual-band absorber with an absorptance of 98.9%at 0.894 THz and 99.9% at 1.408 *** addition,the absorber is polarization insensitive and keeps good performance at large angles of *** the bottom VO_(2) is in an insulating state,the metasurface shows electromagnetically induced *** transparent window can be dynamically regulated by controlling the chemical potential of *** proposed metasurface exhibits the advantages of terahertz absorption,electromagnetically induced transparency and dynamic control,which provides more options for the design of terahertz devices in the future.

关键词： metasurface switchable terahertz absorber electromagnetically induced transparency

Wetting patterns and bacterial distributions in different soils from a surface point source applying effluents with varying Escherichia coli concentrations

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Journal of Integrative Agriculture 2016年第7期15卷 1625-1637页

作者： wen Jie LI jiu-sheng LI Yan-feng State Key Laboratory of Simulation and Regulation of Water Cycle in River basin China Institute of Water Resources andHydropower ResearchBeijing 100048P.R.China

Understanding bacterial transportation in unsaturated soil is helpful for reducing and avoiding pathogenic contamination that may be induced by irrigation with reclaimed waste water and for developing better irrigation management practic-es. Experiments were conducted to study the transport of a typical bacterium,Escherichia coli （E. coli）, in a sandy and a sandy loam soil under different application rates and input concentrations. A 30° wedge-shaped plexiglass container was used to represent one twelfth of the complete cylinder in the experiments. The apparent cylindrical application rate varied from 1.05 to 5.76 L h–1 and the input concentration ofE. coli from magnitude of 102 to 107 colony-forming unit （CFU） mL–1. For a given volume of water applied, an increase in application rate resulted in an increase in the wetted radius and a decrease in the wetted depth. In the sandy loam soil, the water spread out in a circular-arc shaped saturated zone on the surface, and the ultimate saturated entry radius increased with the application rate. An increasing application rate of water suspended bacteria alowed a more rapid transport of bacteria, thus acceleratingE. coli transport rate and resulting in a larger distributed volume ofE. coli for both soil types. For the sandy soil, more than 70% of theE. coli that was de-tected within the entire wetted volume concentrated in the range of 10 cm from the point source, and the concentration of E. colidecreased greatly as the distance from the point source increased. More than 98% of theE. coli was detected in a range of 5 cm around the saturated wetted zone for the sandy loam soil. For both soil types tested, an extremely high concentration ofE. coli was observed in the proximity of the point source, and the peak value increased with an increased input concentration. In principle, using an emitter with relative lower application rate would be effective to restrictE. coli transport. To reduce bacterial concentration in the sewage

关键词： application rate drip irrigation Escherichia coli input concentration

Plant-Wide Supply-Demand Forecast and Optimization of Byproduct Gas System in Steel Plant

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Journal of Iron and Steel Research International 2013年第9期20卷 1-7页

作者： SUN wen-qiang CAI jiu-ju SONG Jun State Environmental Protection Key Laboratory of Eco-Industry Institute of Thermal and Environmental EngineeringNortheastern University School of Mechanical and Power Engineering Henan Polytechnic University

Considerable energy is consumed during steel manufacturing process. Byproduct gas emerges as secondary energy in the process; however, it is also an atmospheric pollution source if it is released into the air. Therefore, the optimal utilization of byproduct gas not only saves energy but also protects environment. To solve this issue, a fore- cast model of gas supply, gas demand and surplus gas in a steel plant was proposed. With the progress of energy conservation, the amount of surplus gas was very large. In a steel plant, the surplus gas was usually sent to boilers to generate steam. However, each boiler had an individual efficiency. So the optimization of the utilization of surplus gas in boilers was a key topic. A dynamic programming method was used to develop an optimal utilization strategy for surplus gas. Finally, a case study providing a sound confirmation was given.

关键词： byproduct gas supply-demand forecast surplus gas dynamic programming method