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Effect of Ce-base mischmetal addition on the microstructure and mechanical properties of hot-rolled ZK60 alloy

Journal of Magnesium and Alloys 2021年第3期9卷 995-1006页

作者： E.P.Silva R.H.Buzolin F.Marques F.Soldera u.alfaro H.C.Pinto Institute of Engineering Science and Technology(IECT)Federal University of Vales do Jequitinhonha e Mucuri(UFVJM)JanaúbaMGBrazil São Carlos School of Engineering(EESC) University of São Paulo(USP)Department of Materials EngineeringCEP 13563-120 São Carlos-SPBrazil Christian Doppler Laboratory for Design of high-performance alloys by thermomechanical processing Kopernikusgasse 24/I8010 GrazAustria Technische universität Graz(Tu Graz) Institute of Materials ScienceJoining and FormingKopernikusgasse 24/I8010 GrazAustria Institute of Functional Materials Department of Materials Science and EngineeringSaarland UniversitySaarbrueckenGermany German Aerospace Center(DLR)Institute of Materials Research Linder Höhe51147 CologneGermany

Mg-Zn-Zr(ZK)alloys exhibit notably high mechanical strength amongst all magnesium alloy ***,due to the formation of low melting point Mg_3Zn_7-precipitates,these alloys are susceptible to hot cracking,thus compromising their metallurgical *** addition of rare earths to ZK alloys is an alternative to form higher melting point intermetallic compounds,speed up dynamic recrystallization,refine grain size,enhance corrosion resistance and extend the service temperature due to improved creep *** work deals with the effect of Ce-base mischmetal addition on the hot rolling behaviour of as-cast ZK60 *** microstructure investigation conducted using electron microscopy and X-Ray diffraction shows that precipitation of Mg_(7)Zn_(3) intermetallics occur during hot rolling,whereas no further precipitation is observed for the ZK60-Mm *** fragmentation of the intermetallic compounds occur during hot rolling and finer particles of Mg_(7)Zn_(3) are observed for the ZK60,whereas Mg_(7)Zn_(3) and Mg Zn_(2) Ce intermetallics are formed in the alloy modified with mischmetal addition.A higher fraction of dynamically recrystallized grains is observed for the ZK60-Mm in comparison to the *** recrystallization takes place in ZK60 with the formation of sub-grains near to the intermetallics and the addition of mischmetal promotes the occurrence of discontinuous recrystallization with the nucleation of new grains close to the *** mechanical strength and,in particular,the ductility of the hot-rolled alloys are notably improved when compared to the same alloys in the as-cast *** mechanical strength is,however,higher for the ZK60 *** solid solution strengthening,softer Mg Zn_(2) Ce intermetallics and more extensive recrystallization contribute to reduce the mechanical strength of *** in both alloys are initiated at coarse intermetallics and propagate through intermetallic-rich regions.

关键词： Magnesium alloys Hot rolling Mischmetal Recrystallization Microstructure Mechanical properties

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Validating a dust production model by field experiment in Mu us Desert, China

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Chinese Science Bulletin 2006年第7期51卷 878-884页

作者： MEI Fanmin J. Rajot S. alfaro L. Gomes ZHANG Xiaoye WANG Tao Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi'an 710075 China Department of Environmental Science and Technology Xi'an University of Engineering and Technology Xi'an 710048 China Center of Monitoring and Forecasting of Chemical Components of Atmosphere State Key Laboratory of Atmospheric Chemistry Institute of National Meteorology Research Beijing 100081 China Laboratoire lnteruniversitaire des Systemes Atmospheriques Universite de Paris 12 Paris 94010 France

Field experiments of dust production have been seldom performed in Chinese deserts that are identified as one of main dust sources in the world, and such an experiment to validate a dust production model (DPM) has not been made in China until now. Saltation flux, dust emission flux, surface features and meteorological parameters (u*, Z0, Ri, etc.) were investigated in Mu us Desert of China to verify the DPM model and accumulate dust emission data during the spring of 2002. It indicates that observed saltation fluxes from 0.07 to 8.00 g·m?1·s?1 are in good agreement with the ones predicted by the DPM model when the constant of the saltation flux equation is tuned to about 2.61, which corresponds to wind fric- tion velocities from 0.26 to 0.35 m·s?1. unfortunately, during three local dust emission events, the observed dust fluxes are from 1 to 3 μg· m?2· s?1, lower than the modeled ones, implying that the model needs to be improved further under lower wind velocity. In comparison with data from a sandy soil with physical crust and a loam soil, saltation fluxes of the loose sandy soil in Mu us Desert are obviously higher, which suggests that deserts and sandy land with desertification are major dust sources in northern China.

关键词：沙漠尘埃模拟野外试验

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Reduction Kinetics of uranium Trioxide to uranium Dioxide using Hydrogen

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World Journal of Nuclear Science and Technology 2015年第3期5卷 149-156页

作者： Pedro Orrego alfaro José Hernández Torres Fernando Puchi Thiele Sección de Geología y Minería Departamento de Materiales Nucleares Comisión Chilena de Energía Nuclear Santiago Chile Ingeniería Civil Metalurgia Universidad Andrés Bello Santiago Chile

This article presents a study on the kinetics of the uranium conversion process, consisting in the reduction of uranium trioxide to uranium dioxide using hydrogen gas at temperatures of 500°C, 600°C and 700°C. Hydrogen concentrations used in the flow were 0.25 M, 0.50 M and 0.75 M. The mechanism established for the study of the kinetics of reduction of uranium trioxide was through the formation of an intermediate compound, u3O8. For this reason, these tests were divided into 2 stages: the first one the reduction from uO3 to u3O8, and second one from u3O8 to uO2. The results of each test were quantified by the release of H2O(g) produced by both reactions. Tests showed that the ideal working conditions are for hydrogen concentration flows of 0.75 M and temperatures in the range of 500°C - 600°C, with the intent to decrease the occurrence of side reactions that interfere with the process.

关键词： Conversion uranium Oxides Nuclear Fuel Cycle

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