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Grain Size Distribution and Interfacial Heat transfer Coefficient during Solidification of Magnesium Alloys Using High Pressure Die Casting Process

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journal of Materials Science & technology 2018年第2期34卷 324-334页

作者： P. Sharifi j. jamali K. Sadayappan j.t. Wood Western University London Ontario Canada Canmet MAtERIALS Hamilton ON Canada

the objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASttM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. the simulation results were used to estimate the centerline cooling curve at various locations through the casting. the centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. the effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. the grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. the prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.

关键词： High pressure die casting Grain size lnterfacial heat transfer coefficient Solidification of magnesium alloys Process parameters

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PREPARAtION OF MESOPOROUS CARBON BY CARBON DIOXIDE ACtIVAtION WItH CAtALYSt

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Acta Metallurgica Sinica(English Letters) 2002年第1期15卷 67-72页

作者： W.Z. Shen A.H. Lu j.t. Zheng Institute of Coal Chemistry The Chinese Academy of Sciences Taiyuan 030001 China

A mesoporous activated carbon (AC) can be successfully prepared by catalytic activation with carbon dioxide. For iron oxide as catalyst, there were two regions of mesopore size distribution, i.e. 2-5nm and 30-70nm. When copper oxide or magnesium oxide coexisted with iron oxide as composite catalyst, the content of pores with sizes of 2-5nm was decreased, while the pores with 30-70nm were increased significantly. For comparison, AC reactivated by carbon dioxide directly was also investigated. It was shown that the size of mesopores of the resulting AC concentrated in 2-5nm with less volume. the adsorption of Congo red was tested to evaluate the property of the result-ing AC. Furthermore, the factors affecting pore size distribution and the possibility of mesopore formation were discussed.

关键词： activated carbon mesopore. catalytic activation

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tHEOREtICAL StUDY OF HEAt tRANSFER ENHANCEMENt IN PIPE WItH POROUS BODY

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journal of Hydrodynamics 2001年第1期13卷 111-116页

作者： Gong, W.P. Han, j.t. Cheng, F. Dep. of Power Eng. Shandong Univ. Jinan 250061 China

A theoretical investigation on the fluid flow and heat transfer in a pipe with porous body of high porosity twisted by metal wire was carried out. A theoretical model of a circular pipe with porous matrix attached at the channel wall and extended inward the centerline was set up. through analyzing the flow in the porous matrix by the Brinkman-extended-Darcy equation and through including the effect of dispersion by adding the dispersion coefficient into the energy equation, the theoretical solutions of velocity distribution and temperature fields were obtained. Finally the effect of the properties of the porous matrix on the flow and heat transfer in the porous body was studied, which indicates that dispersion can really enhance the heat transfer in pipe.

关键词： Computer simulation Dispersions Mathematical models Pipe flow Porosity Porous materials

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Performance and calibration of quark/gluon-j.t.taggers using 140 fb^(-1) of pp collisions at √s=13 teV with the AtLAS detector

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Chinese Physics C 2024年第2期48卷 1-25页

作者： G. Aad B. Abbott K. Abeling N.j. Abicht S.H. Abidi A. Aboulhorma H. Abramowicz H. Abreu Y. Abulaiti B.S. Acharya C. Adam Bourdarios L. Adamczyk S.V. Addepalli M.j. Addison j. Adelman A. Adiguzel t. Adye A.A. Affolder Y. Afik M.N. Agaras j. Agarwala A. Aggarwal C. Agheorghiesei A. Ahmad F. Ahmadov W.S. Ahmed S. Ahuja X. Ai G. Aielli A. Aikot M. Ait tamlihat B. Aitbenchikh I. Aizenberg M. Akbiyik t.P.A. Åkesson A.V. Akimov D. Akiyama N.N. Akolkar K. Al Khoury G.L. Alberghi j. Albert P. Albicocco G.L. Albouy S. Alderweireldt M. Aleksa I.N. Aleksandrov C. Alexa t. Alexopoulos F. Alfonsi M. Algren M. Alhroob B. Ali H.M.j. Ali S. Ali S.W. Alibocus M. Aliev G. Alimonti W. Alkakhi C. Allaire B.M.M. Allbrooke j.F. Allen C.A. Allendes Flores P.P. Allport A. Aloisio F. Alonso C. Alpigiani M. Alvarez Estevez A. Alvarez Fernandez M. Alves Cardoso M.G. Alviggi M. Aly Y. Amaral Coutinho A. Ambler C. Amelung M. Amerl C.G. Ames D. Amidei S.P. Amor Dos Santos K.R. Amos V. Ananiev C. Anastopoulos t. Andeen j.K. Anders S.Y. Andrean A. Andreazza S. Angelidakis A. Angerami A.V. Anisenkov A. Annovi C. Antel M.t. Anthony E. Antipov M. Antonelli F. Anulli M. Aoki t. Aoki j.A. Aparisi Pozo M.A. Aparo L. Aperio Bella C. Appelt A. Apyan N. Aranzabal S.j. Arbiol Val C. Arcangeletti A.t.H. Arce E. Arena j-F. Arguin S. Argyropoulos j.-H. Arling O. Arnaez H. Arnold G. Artoni H. Asada K. Asai S. Asai N.A. Asbah j. Assahsah K. Assamagan R. Astalos S. Atashi R.j. Atkin M. Atkinson H. Atmani P.A. Atmasiddha K. Augsten S. Auricchio A.D. Auriol V.A. Austrup G. Avolio K. Axiotis G. Azuelos D. Babal H. Bachacou K. Bachas A. Bachiu F. Backman A. Badea P. Bagnaia M. Bahmani A.j. Bailey V.R. Bailey j.t. baines L. baines O.K. Baker E. Bakos D. Bakshi Gupta V. Balakrishnan R. Balasubramanian E.M. Baldin P. Balek E. Ballabene F. Balli L.M. Baltes W.K. Balunas j. Balz E. Banas M. Bandieramonte A. Bandyopadhyay S. Bansal L. Barak M. Barakat E.L. Barberio D. Barberis M. Barbero M.Z. Barel K.N. Barends t. Barillari M-S. Barisits t. Barklow P. Baron D.A. Baron Mo the AtLAS Collaboration

the identification of j.t. originating from quarks and gluons,often referred to as quark/gluon tagging,plays an important role in various analyses performed at the Large Hadron Collider,as Standard Model measurements and searches for new particles decaying to quarks often rely on suppressing a large gluon-induced *** paper describes the measurement of the efficiencies of quark/gluon taggers developed within the AtLAS Collaboration,using √s=13 teV proton–proton collision data with an integrated luminosity of 140 fb^(-1) collected by the AtLAS *** taggers with high performances in rejecting j.t. from gluon over j.t. from quarks are studied:one tagger is based on requirements on the number of inner-detector tracks associated with the j.t.and the other combines several j.t.substructure observables using a boosted decision tree.A method is established to determine the quark/gluon fraction in data,by using quark/gluon-enriched subsamples defined by the j.t.*** in tagging efficiency between data and simulation are provided for j.t. with transverse momentum between 500 GeV and 2 teV and for multiple tagger working points.

关键词： AtLAS jEt QUARK GLUON tAGGING

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EFFECtS OF CHEMICAL MODIFICAtIONS AND MMt NANOCLAY ADDItION ON tRANSPORt PHENOMENA OF NAtURALLY WOVEN COCONUt SHEAtH/POLYEStER NANOCOMPOSItES

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Chinese journal of Polymer Science 2013年第8期31卷 1074-1086页

作者： N. Rajini j.t. Winowlin jappes S. Rajakarunakaran C. Bennet Centre for Composite Materials Department of Mechanical Engineering Kalasalingam University Center for Advanced Materials Department of Mechanical Engineering Cape Institute of Technology Levengipuram

Studies on the behavior of molecular transport properties such as thermal conductivity, gas permeability, volume and surface resistivity have been carried out for the naturally woven coconut sheath （CS） fiber reinforced composites with the addition of nanoclay and chemical treatment of fiber. the compression molding technique was used to fabricate the coconut sheath/clay reinforced hybrid composites. the morphological studies such as X-ray diffractogram （XRD）, transmission electron microscopy （tEM） and scanning electron microscopy （SEM） have been carried out for polyester nanocomposites and coconut sheath fiber. the decreased gas permeability, thermal conductivity and volume and surface resistivity have been observed with increasing the weight percentage of nanoclay in polyester matrix. In chemical modifications, the alkali and silane treated coconut sheath reinforced composites have shown great influence on the transport properties due to the increasing hydrophilic nature by the topographical changes at the fiber surface. Dielectric strength has also been reported in this paper for all types of composites. Infra-red （IR） spectra have also been taken to study the physical and chemical structural changes of treated coconut sheath.

关键词： Nanoclay Coconut sheath Gas permeability tEM SEM FtIR.

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Solid particle erosion studies of thermally deposited alumina-titania coatings on an aluminum alloy

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International journal of Minerals,Metallurgy and Materials 2021年第7期28卷 1186-1193页

作者： Chellaganesh Duraipandi Adam Khan M Winowlin jappes j.t. Nouby MGhazaly Peter Madindwa Mashinini School of Automotive and Mechanical Engineering and Centre for Surface Engineering Kalasalingam Academy of Research and EducationKrishnankoil 626126VirudhunagarTamilnaduIndia Mechanical Engineering Department Faculty of EngineeringSouth Valley UniversityQena 83523Egypt Department of Mechanical and Industrial Engineering technology University of JohannesburgDoornfontein CampusJohannesburg 2028South Africa

thermal barrier coatings are widely used as surface modifications to enhance the surface properties of the material and protect from surface degradations such as erosion and ***-based coatings are highly recommended to increase wear resistance in the indus-trial *** this paper,an alumina-titania ceramic powder was deposited on an aluminum alloy using an atmospheric plasma spray *** investigations were performed to study the behavior and erosion rate of the *** particle erosion studies were performed by varying the particle velocity and particle flow *** angle impingement and stand-off distance were constant for *** base metal has a clinging effect and the mass change was negative at a maximum particle flow rate of 4 g·min^(−1).Under the same process conditions,the coated sample had a reduced lifetime and reached a maximum erosion rate of 0.052(Δg/g).the solid particle erosion studies confirmed that the base metal aluminum alloy had severe surface damage with erodent reinforcement when compared to the coated *** influence of the particle velocity,particle flow rate,and input process parameters were also identified.

关键词： erosion alumina wear velocity microstructure

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SUPERPLAStICItY OF A Ni-28.5Al-20.4Fe INtERMEtALLIC ALLOY

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Acta Metallurgica Sinica(English Letters) 2000年第3期13卷 888-892页

作者： Zhou, W.L. Guo, j.t. Chen, R.S. Zhou, j.Y. Inst of Metal Research Chinese Acad of Sciences Shenyang China

Our previous investigation examined the superplastic behavior of an extruded Ni-28.5Al-20.4Fe alloy. Its tensile properties were determined at temperature from 1123 K to 1323 K and initial strain rates from 1.04×10-2s-1 to 1.04×10-4s-1. A maximum elongation of 233% was obtained at 1123 K and a strain rate of 5.2×10-4s-1. Furthermore, microstructural features, such as decrease in the average grain size after deformation at 850 °C and 980 °C, the presence of many dislocation-free grains adjacent to grains with a high dislocation density, indicate that dynamic recrystallization has occurred as an efficient accommodation mechanism. SEM examination of the fracture sample after superplastic deformation reveals many voids on the fracture surface. By correlating with the result of tEM observation, it is suggested that the superplastic deformation in this alloy should be controlled by a grain boundary sliding-based mechanism accommodated by the movement of dislocation and dynamic recrystallization.

关键词： Activation energy Aluminum alloys Intermetallics Iron alloys Microstructure Recrystallization (metallurgy) Superplasticity tensile testing

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INFLUENCE OF SILICON IN StEELS ON GALVANIZED COAtINGS

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Acta Metallurgica Sinica(English Letters) 2006年第2期19卷 85-90页

作者： C.S. Che j.t. Lu G. Kong Q.Y. Xu j.H. Chen College of Materials Science and Engineering South China University of Technology Guangzhou 510640 China

After steel sheets （0.37wt%Si） pre-electroplated with a thin layer of pure Fe were immersed in molten zinc for various time, the change in the microstructure of the galvanized coating on the steel and the change of α-Fe/Г interface were studied. the EDS （energy dispersive sepectroscopy） resuits show that excessive silicon accumulates on the surface of the steel substrate due to the low solubility of silicon in the Г layer after the Fe layer is depleted by the increasing growth of the compound layers. With the movement of α-Fe/Г interface towards the substrate by the Fe/Zn reaction, silicon-rich α-Fe peels off from the substrate and breaks into particles. the particles, much like an inert marker in a Kirkendall effect experiment, move towards the δ layer through the Г layer because silicon-rich α-Fe can not be adsorbed in the Г layer. On reaching the 8/F interface, the particles quickly dissolve in the δ layer, and accelerate its growth, resulting in the gradual disappearance of the Г layer. At the same time, the normal coating is quickly changed into coatings typical of reactive steels as silicon dissolved in the δ layer soon diffuses toward the ζ layer. A similar process may happen in the initial stage of galvanizing reactive steels on a small scale, although it is hard to be observed.

关键词： Zn coating intermetallics steel electrodeposition

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Comparison of artificial neural networks with empirical correlations for estimating the average cycle time in conical spouted beds

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Particuology 2019年第1期17卷 48-57页

作者： I. Estiatia M. tellabidea j.F. Saldarriaga H. Altzibara F.B. Freirec j.t. Freirec M. Olazara Department of Chemical Engineering University of the Basque CountryP.O. box 644E48080 BilbaoSpain Department of Civil and Environmental Engineering Universidad de los AndesCr.1 Este 19A-40BogotaColombia Department of Chemical Engineering Federal University of Sao CarlosRod. Washington Luis-km 235P.O. box 67613565-905Sao CarlosSPBrazil

Conventional spouted beds have been extensively used in many real-life applications but are not suited for all types of materials, especially fine particles, which require internal devices to improve their motion in the spouted bed. However, unlike conventional spouted beds, there are almost no mechanistic or empirical models available for the design of spouted beds with internals. Given the availability of an extensive but not experimentally designed database, the main purpose of this study is to present an analysis of neural networks and empirical models in terms of their suitability to fit and predict average cycle times in conical spouted beds with and without draft tubes. the parameters investigated are particle size, density, contactor angle, gas inlet diameter, static bed height, and draft tube features. Although the amount of information is always a key factor when fitting models, the size of the database used in this study strongly affects the fitting performance of empirical models, whereas artificial neural networks are more influenced by how the data are scaled. Results of model verification show that both techniques are suitable for predicting average cycle times for data outside the range covered by the database.

关键词： Empirical correlation Artificial neural network Average cycle time Conical spouted bed Draft tubes Modeling

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ALLOYING EFFECt OF Ni AND Cr ON tHE WEttABILItY OF COPPER ON W SUBStRAtE

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Acta Metallurgica Sinica(English Letters) 2008年第5期21卷 369-379页

作者： X.H. Yang P. Xiao S.H. Liang j.t. Zou Z.K. Fan Shaanxi Key Laboratory for Electrical Materials and Infiltration technology School of Materials Science and Engineering Xi＇an University of Technology Xi＇an 710048 China

By the sessile drop technique, the wettability of Cu/W systems with the additions of Ni and Cr has been studied under vacuum atmosphere. Effects of Ni and Cr contents and wetting temperatures on the wettability and the wetting mechanisms of copper on W substrate have been investigated in detail. the results show that the wetting angles of Cu on the W substrate are decreased with an increase in the content of Ni or Cr, and also decrease with raising the wetting temperatures. SEM, EPMA, and X-ray diffraction have been used to analyze the interracial characteristics of the CuNi/W and CuCr/W systems. the results reveal that there is a transition layer about 2- 3μm in the interface of Cu-4.0 wt pct Ni/W, in which the interrnetallic phase Ni4W is precipitated. As to CuCr/W system, no reaction occurs at the interface. the two factors are that the contents of Cr and Ni and the infiltration temperature must be chosen appropriately in order to control the interfacial dissolution and reaction when the Cu- W alloys are prepared by the infiltration method.

关键词： Wettability Contact angles Cu, Cr, Ni W substrate

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