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microstructural Evolution of Solid-solution-treated zn-22Al in the Semisolid State

Journal of materials Science & Technology 2013年第8期29卷 765-774页

作者： m.A.m.Arif m.z.Omar n.muhamad J.Syarif P.kapranos Department of mechanical and materials Engineering Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia43600 BangiSelangorMalaysia Department of materials Science and Engineering The University of SheffieldSir Robert Hadfield BuildingMappin St.Sheffield S1 3JDUK

The effect of solid-solution-treatment on the semisolid microstructure of zn-22Al with developed dendrites was investigated. Forming zn-22Al products by semisolid metal processing offers significant advantages, such as reductions in macro-segregation, porosity and forming costs. Thermal and rnicrostructural analyses of the formed zn-22Al alloy were performed by differential scanning calorimetry, scanning electron microscopy and optical microscopy. The changes in the microstructures and phase transformation in response to various solid- solution-treatments were analysed. In this study, as-cast samples were held isothermally at 330 ℃ for 0.5- 5 h and then partially remelted at a semisolid temperature of 438 ℃ for 1 h to produce a solid-globular grain structure in a liquid matrix. A non-dendritic semisolid microstructure could not be obtained when the traditionally cast zn 22Al alloy with developed dendrites was subjected directly to partial remelting. After solid-solution-treatment at 330 ℃, the black interdendritic eutectics were dissolved, and the dendritic structures gradually transformed into uniform β structures when the treatment time was increased. The coarsened and merged dendrites were separated as a result of penetration by the liquid phase and melting of the residual eutectic at sites along the former grain boundaries. The microstructure of the solid-solution- treated sample transformed into a small globular structure; the best shape factor of 0.9, corresponding to a particle size of 40 ± 16 μm, is achieved when the sample was treated for 3 h followed by direct partial remelting into its semisolid zone.

关键词： Semisolid metal processing Solidus liquidus Dendritic Spherical morphologies

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Design optimisation for distance between additional and tap winding in high-voltage transformers

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High Voltage 2020年第6期5卷 716-723页

作者： kamran Dawood Ahmet kerem köseoğlu Güven kömürgöz Department of Electrical Engineering Istanbul Technical UniversityIstanbulTurkey Best Transformers BalıkesirTurkey

The transformer is one of the main components in the power network and transformer windings are one of the most expensive elements in the power transformer. Optimisation of winding distances is one of the most important parameters during the manufacturing of transformer. The distance between the windings in the two winding transformers is well known to transformer designers and manufacturers. However, insulation of the high voltage transformer with additional winding and tap winding is still a major problem for transformer designers. In this study, the additional winding to tap winding distance optimisation is made for a high voltage power transformer. Optimisation of the transformer's windings just not minimises the cost of the transformer but also increases the lifetime of the transformer. With additional winding and tap winding in high-voltage transformers, insulation distance is a major concern for minimising the cost and size of the high voltage transformer. In this study, an approach is made to balance the cost, size, and safety of high voltage transformers. The optimised distance and position between tap winding and additional winding are determined by using the finite element analysis. The finite element method results were also verified by making a prototype transformer.

关键词： winding insulation high

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Thin-shell wormholes and modified Chaplygin gas with relativistic corrections

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Communications in Theoretical Physics 2023年第12期75卷 84-96页

作者： m.z.Bhatti z Yousaf m Yousaf Department of mathematics University of the PunjabQuaid-i-Azam CampusLahore-54590Pakistan

In this paper,we analyze thin-shell wormholes from two identical copies of charged static cylindrically symmetric spacetimes using Visser’s‘cut and paste’approach under the influence of f(R,T)gravity Harko,lobo,nojiri,and Odintsov(2011,***.D 84,024020).In this scenario,the modified Chaplygin gas supports the exotic matter in the shell which allows,one to examine the dynamics of constructed *** utilize the junction condition to connect the interior and exterior geometries across the hypersurface and calculate different components of the lanczos equation recently computed by Roza in Rosa(2021,***.D 103,104069).We analyze the stability of the thin-shell wormhole models under linear perturbations while keeping the cylindrical symmetry and also examine the influence of charge on their *** positive quantity of the second derivative of potential at the throat radius might be interpreted as the stability *** find both unstable and stable wormhole solutions for different parameters included in the equation of state and specific forms of considered gravity and illustrate them theoretically as well as *** examine the impact of electric charge on the stability region of a constructed wormhole,which suggests that a wormhole model with a charge may exhibit more stable behavior compared to an uncharged system.

关键词： wormholes gravitation mathematical and relativistic aspects of cosmology

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Complexity of charged anisotropic spherically symmetric fluids in f(G)gravity

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Communications in Theoretical Physics 2023年第3期75卷 91-104页

作者： z Yousaf m.z.Bhatti m m m nasir Department of mathematics University of the PunjabQuaid-i-Azam CampusLahore-54590Pakistan

The previous ideology of complexity factor for the dynamical spheres[Herrera et al 2018,***.D,98,104059]is extended for the influence of charge.A dynamical spherically symmetric non-dissipative and dissipative self-gravitating structure is examined in the presence of maxwell f(G)gravity to examine the complexity *** pattern of evolution is studied with the minimal complexity *** complexity factor remains the same for the structure of fluid distribution,while we examine homologous constraints for the most basic evolution *** calculate the structure scalars which play an important role in order to understand the fundamental properties of the *** fluid is geodesic as well as shearing for the dissipative case and there is a large number of *** the non-dissipative fluid distribution,a shear-free,homogeneous and isotropic,geodesic fluid correlates with the evolving homologous and vanishing complexity *** implication of the condition of vanishing complexity factor and stability are discussed at the end.

关键词： gravitation anisotropy complexity hydrodynamics

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An Analysis of Peristaltic Flow of a micropolar Fluid in a Curved Channel

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Chinese Physics letters 2011年第1期28卷 138-141页

作者： n. Ali m. Sajid T. ,laved z. Abbas Department of mathematics International Islamic University Islamabad Paksitan Theoretical Plasma Physics Division PINSTECH P.O. Nilore Islamabad Pakistan

We analyze the two-dimensional peristaltic flow of a micropolar fluid in a curved channel. long wavelength and low Reynolds number assumptions are used in deriving the governing equations. A shooting method with fourth-order Runge-kutta algorithm is employed to solve the equations. The influence of dimensionless curvature radius on pumping and trapping phenomena is discussed with the help of graphical results. It is seen that the pressure rise per wavelength in the pumping region increases with an increase in the curvature of the channel. moreover the symmetry of the trapped bolus destroys in going from strmg＇ht to curved channel.

关键词： Fluid dynamics

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Stretching a Curved Surface in a Viscous Fluid

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Chinese Physics letters 2010年第2期27卷 149-152页

作者： m. Sajid n. Ali T. Javed z. Abbas Theoretical Plasma Physics Division PINSTECH P.O. Nilore Islamabad 44000 Pakistan Faculty of Basic and Applied Sciences International Islamic University Islamabad 44000 Pakistan

This work is concerned with the viscous flow due to a curved stretching sheet. The similarity solution of the problem is obtained numerically by a shooting method using the Runge-kutta algorithm. The physical quantities of interest like the fluid velocity and skin friction coefficient are obtained and discussed under the influence of dimensionless curvature. It is evident from the results that dimensionless curvature causes an increase in boundary layer thickness and a decrease in the skin friction coefficient.

关键词： Fluid dynamics mathematical physics

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magnetic properties of Sn-substituted ni-zn ferrites synthesized from nano-sized powders of niO, znO, Fe2O3, and SnO2

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Chinese Physics B 2017年第7期26卷 377-382页

作者： m A Ali m m Uddin m n I khan F U z Chowdhury S m Hoque S I liba Department of Physics Chittagong University of Engineering and Technology (CUET) materials Science Division Atomic Energy Center

A series of ni0.6-x/2zn0.4-x/2SnxFe2O4(x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3)(nzSFO) ferrite composities have been synthesized from nano powders using a standard solid state reaction technique. The spinel cubic structure of the investigated samples has been confirmed by x-ray diffraction(XRD). The magnetic properties such as saturation magnetization(ms),remanent magnetization(mr), coercive field(Hc), and Bohr magneton(μ) are calculated from the hysteresis loops. The value of msis found to decrease with increasing Sn content in the samples. This change is successfully explained by the variation of A-B interaction strength due to Sn substitution in different sites. The compositional stability and quality of the prepared ferrite composites have also been endorsed by the fairly constant initial permeability(μ’) over a wide range of frequency. The decreasing trend of μ’ with increasing Sn content has been observed. Curie temperature TChas been found to increase with the increase in Sn content. A wide spread frequency utility zone indicates that the nzSFO can be considered as a good candidate for use in broadband pulse transformers and wide band read-write heads for video recording. The composition of x = 0.05 shows unusual results and the possible reason is also mentioned with the established formalism.

关键词： magnetic properties saturation magnetization permeability Curie temperature

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Effect of Y Addition on microstructure and mechanical Properties of Friction Stir Welded zk60 Alloy

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Journal of materials Science & Technology 2009年第3期25卷 351-355页

作者： G.m. Xie z.Y. ma l. Geng School of materials Science and Engineering Harbin Institute of Technology Harbin 150001 China Shenyang national laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

6 mm thick zk60 and zk60-Y alloy plates were successfully friction stir welded （FSW） at a tool rotation rate of 1200 r/min and a traverse speed of 100 mm/min. FSW resulted in the dissolution of m.z.2 particles in the zk60 and the breakup and dispersion of W-phase （mg3zn3Y2） particles in the zk60-Y alloy, thereby leading; to a decrease in the hardness of the nugget zone （nz） for the zk60 alloy and an increase in the hardness of the nz for the zk60-Y alloy, respectively. While two FSW joints exhibited similar joint efficiency （87%-89% of ultimate tensile strengths of the parent materials）, the yield strength of the FSW zk60-Y joint was substantially higher than that of the FSW zk60 joint. The fracture occurred in the nz and the heat affected zone for the zk60 and zk60-Y joints, respectively, which were consistent with the lowest hardness distribution of the welded joints.

关键词： Friction stir welding magnesium microstructure mechanical properties

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Comparing hydrogen embrittlement behaviors of two press hardening steels:2 GPa vs.1.5 GPa grade

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Journal of materials Science & Technology 2022年第29期124卷 109-115页

作者： z.H.Cao B.n.zhang m.X.Huang Department of mechanical Engineering The University of Hong KongPokfulam RoadHong KongChina

*** The pursuit of advanced high-strength steels(AHSS)has been rising for the automobile industry to build lightweight and fuelefficient vehicles without compromising crashworthiness[1,2].The group of press hardening steels(PHS)is an excellent candidate that comprises high strength,high toughness,and good formability,which are optimal to build intrusion resistant components such as(ⅰ)A/B-pillar reinforcements,(ⅱ)bumper and door beams.

关键词： strength toughness steels

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mECHAnISm AnD kInETICS OF TRAnSFORmATIOn OF AlUmInA InClUSIOnS BY CAlCIUm TREATmEnT

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Acta metallurgica Sinica(English letters) 2006年第1期19卷 1-8页

作者： z.J. Han l. liu m. lind l. Holappa Central Iron and Steel Research Institute Beijing 100081 China laboratory of metallurgy Helsinki University of Technology P.O. Box 6200Espoo 02015 Finland

The basic mechanism and kinetics of the transformation process of alumina inclusions in steel was reported when calcium introduced into the steel by wire feeding orpowder injection. To clarify the mechanisms model, experiments were performed by studying reactions between AltOs and CaO in a laboratory furnace and by performing calcium treatments in an 8kg induction furnace for Al deoxidised melt. The phases formed during the reaction between Al2O3 and CaO were examined by SEm-EDS （scanning electron microscope-energy dispersive spectrometer）, and the reaction sequence of Al2O3=〉 CA6=〉 CA2 =〉 CA =〉 CAx（l） was discussed in term of the experimental observations. The kinetics of the reaction of calcium with alumina inclusions were simulated by immersing alumina plates in a Ca treated steel melt in the induction furnace. Results were compared with observations of real inclusion transformation. A kinetic model was proposed based on the results.

关键词： mechanism kinetics alumina inclusion transformation

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