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Precipitation behaviors and mechanical properties of a solution-treated Mg-Gd-Nd-Zn-Zr alloy during equal-channel angular pressing process

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Journal of Magnesium and Alloys 2022年第1期10卷 257-266页

作者： Zhenzhen Gui Fen Wang Junyi Zhang Dexin Chen Zhixin Kang School of Mechanical and Electrical Engineering Guangzhou University230 Wai Huan Xi RoadGuangzhou Higher Education Mega CenterGuangzhou 510006China Guangdong Key Laboratory for Advanced Metallic Materials Processing School of Mechanical and Automotive EngineeringSouth China University of TechnologyGuangzhou 510640China Institute of Advanced Wear&Corrosion Resistant and Functional Materials Jinan University601 Hmmgpu Avenue WestGuangzhou 510632China

A magnesium alloy processed by equal-channel angular pressing (ECAP) exhibited excellent microstructure refinement and improved strength and hardness.The comprehensive mechanical properties of magnesium alloys have supported the expansion of their applications in the automotive,aerospace,and biomedical industries.Herein,pre-treatment of a solution-treated Mg-2.9Gd-1.5Nd-0.3Zn-0.3Zr alloy was conducted to investigate the precipitate behavior and microstructure evolution during the ECAP process.β;phase grains quickly precipitated from the solution-treated alloy,which accelerated grain refinement and enhanced the ductility after the ECAP process,as compared to the as-cast alloy reported in our previous study.Moreover,spherical precipitates (~200 nm) and fine phases (~100 nm) precipitated along the stripe-like Zn;Zr;phase,which formed a kabap-like structure dispersing homogeneously in the solution-treated alloy during the ECAP process.Owing to grain refinement,dislocations,sphericalβ;precipitates,and texture evolution,the solution-treated alloy after eight passes of ECAP exhibited good comprehensive mechanical properties,with the ultimate tensile strength,yield strength,and elongation values reaching210.9 MPa,263.9 MPa,and 27.9%,respectively.

关键词： Mg-Gd-Nd-Zn-Zr alloy precipitations Solid solution ECAP Mechanical properties

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Age hardening responses of as-extruded Mg-2.5Sn-1.5Ca alloys with a wide range of Al concentration

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Journal of Materials Science & Technology 2020年第3期38卷 39-46页

作者： Qiuyan Huang Yang Liu Aiyue Zhang Haoxin Jiang Hucheng Pan Xiaohui Feng Changlin Yang Tianjiao Luo Yingju Li Yuansheng Yang Institute of Metal Research Chinese Academy of SciencesShenyang110016China Key Laboratory for Anisotropy and Texture of Materials(MOE) School of Materials Science and EngineeringNortheastern UniversityShenyang110819China Research Center for Metallic Wires Northeastern UniversityShenyang110819China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China

This article aims to explore the age hardening responses of both as-extruded and as-aged Mg-2.5 Sn-1.5 Ca-x Al alloys(x=2.0,4.0 and 9.0 wt%,termed TXA322,TXA324 and TXA329,respectively)through microstructural and mechanical characterization.Results indicate that grain size of as-extruded TXA322,TXA324 and TXA329 alloys were^16μm,~10μm and^12μm,respectively.A number ofanddislocations were observed in all the as-extruded samples.Guinier–Preston(GP)zones were evidently identified in TXA322 alloy,while only a small number of Mg17 Al12 phases existed in both TXA324 and TXA329 alloys.An aging treatment facilitated the precipitation of a high number density of GP zones within the matrix of TXA322 alloy.In contrast,no obvious nano-precipitates were in as-aged TXA324 alloy.Numerous nano-Mg17 Al12 phases were formed through a following aging treatment in TXA329 alloy.In terms of mechanical properties,it is apparent that an increment in ultimate tensile strength of^46 MPa and^40 MPa was yielded in peak-aged TXA322 and TXA329 alloys,while no obvious variations in UTS were present in peak-aged TXA324 alloy,in comparison with the as-extruded counterparts.

关键词： Magnesium alloys Age hardening precipitations Dislocations Mechanical properties

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Evaluation of Eta Weather Forecast Model over Central Africa

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Atmospheric and Climate Sciences 2012年第4期2卷 532-537页

作者： Romeo Steve Tanessong Derbetini A. Vondou P. Moudi Igri F. Mkankam Kamga Laboratory for Environmental Modelling and Atmospheric Physics Department of Physics University of Yaounde 1 Yaounde Cameroon

The main goal of this work is to investigate the skills of Eta weather forecast model in forecasting precipitations, temperature and sea level pressure. The model domain extends from 6°W to 29°E and 6°S to 21°N. The model is run with a horizontal resolution of 48 km with 45 vertical levels and initial and boundary conditions were given by National Centers for Environmental Prediction (NCEP) 00UTC operational analysis. All the forecasts are for period of 48 hours. They were compared to the Tropical Rainfall Measuring Mission (TRMM) derived data for precipitations and NCEP/NCAR (National Center for Atmospheric Research) analysis for temperature and sea level pressure. The results show that Eta model predicts fairly good 2 meters temperature and the sea level pressure. Spatial distributions of precipitations are not well simulated by the model.

关键词： precipitations Temperature Sea Level Pressure Eta Model

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Solar Activity and Meteorological Fluctuations in West Africa: Temperatures and Pluviometry in Burkina Faso, 1970-2012

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International Journal of Astronomy and Astrophysics 2013年第4期3卷 408-411页

作者： Jean-Louis Zerbo Frédéric Ouattara Emmanuel Nanéma LERSEM University of Koudougou Koudougou Burkina Faso UFR/ST Polytechnic University of Bobo Dioulasso Bobo-Dioulasso Burkina Faso

In this paper we investigate the fluctuations of solar activity and their links with climatic parameters in West Africa. We achieve our research by investigating several data plotted using averages. Mean to our results we can assume that active solar is associated with weak incident cosmic ray consequently with low cloudiness which brings warming. Likewise, quiet solar is associated with important cloud cover and consequently brings important precipitations and chills terrestrial atmosphere. This implies the necessity to deal with space phenomenon by considering the severe interconnection between solar activity indices for interplanetary and earth environment weather forecasting.

关键词： Solar Activity Temperatures precipitations Cloud Cover Solar Cycle

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VARIABILITY OF DAILY PRECIPITATION IN CHINA(1980-1993): PCA AND WAVELET ANALYSIS OF OBSERVATION AND ECMWF REANALYSIS DATA

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Chinese Journal of Oceanology and Limnology 2000年第2期18卷 117-110,118-125页

作者：崔茂常朱海练树民 KlausArpe LydiaDümenil 中科院海洋所大气科学和地球流体力学数值模拟国家重点实验室山东青岛 2 660 71 中科院大气物理所大气科学和地球流体力学数值模拟国家重点实验室北京 1 0 0 0 2 中科院海洋所山东青岛 2 660 71 Max- Planck-Institute for Meteorology 德国

In this study, principal component analysis(PCA) and complex Morlet wavelet transform were used with daily rainfall in China for the period 1980-1993(1 May-31 Dec.) from observation and ECMWF reanalysis to study its variability and evaluate the validation of reanalyzed precipitation. The results showed that northward movement of the summer rain belt was a wavelike propagation, which was always accompanied by rainfall breaks and could be treated as one event under time scale of about 1 month only. The first 4 EOFs accounted for 28% and 35% of total variance from observation and reanalysis, respectively, and were roughly consistent with each other. The first and third EOFs for observation mainly represented interweekly, interseasonal and interannual variations and contained some summer intraseasonal fluctuations also. The second and fourth ones mainly represented some rather strong summer intraseasonal fluctuations for a paticular year and contained interweekly, interseasonal and interannual variations also. Although there is still room for improvement, the ECMWF reanalysis is the best available dataset with global coverage and daily variability.

关键词： daily precipitations in China ECMWF reanalysis PCA and wavelet analysis

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