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incipient plasticity and activation volume of dislocation nucleation for TiZrNbTaMo high-entropy alloys characterized by nanoindentation

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Journal of Materials Science & Technology 2019年第5期35卷 812-816页

作者： Shao-Ping Wang Jian Xu Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences 72 Wenhua Road Shenyang 110016 China University of Chinese Academy of Sciences 19(A) Yuquan Road Beijing 100049 China

With instrumented nanoindentation, incipient plasticity of two as-cast BCC TiZrNbTa and TiZrNbTaMo high-entropy alloys(HEAs) are investigated in terms of pop-in events during loading, to characterize the dislocation behavior in these solid-solution alloys. It is shown that the maximum shear stress (max)required for dislocation nucleation is determined to be 1/16-1/12 and 1/18-1/14 of shear modulus for the TiZrNbTa and TiZrNbTaMo HEAs, respectively, which is nearly comparative to the theoretical shear stress of these alloys. The activation volumes of dislocation nucleation the TiZrNbTa and TiZrNbTaMo HEAs are determined to be 1.2 b^3 for and 1.3 b^3, respectively, which is substantially irrespective of alloying with Mo. Furthermore, activation volumes of these two HEAs are on the order of cubic burger’s vector and only one-third of the value for TiZrHfNb HEA, suggesting that a heterogeneous nucleation of dislocation took place in a way of direct atom-vacancy exchange, rather than of the cooperative motion of several atoms. These findings reveal the unique feature in deformation of BCC solid-solution complex alloys.

关键词： High-entropy alloys Nanoindentation Refractory metals BCC phase incipient plasticity

incipient charnockites from southern India:The role of brines

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Geoscience Frontiers 2019年第5期10卷 1789-1801页

作者： Jacques L.R. Touret Robert C. Newton Michel Cuney 121 Rue de la Réunion F-75020ParisFrance Department of Earth Planetary and Space SciencesUCLALos AngelesCAUSA Université de Lorraine CNRS-CREGUGeoRessources BP70239F-54506Vandoeuvre-les-Nancy CedexFrance

Southern India and Sri-Lanka are the places where “incipient charnockites”,i.***.the local transformation of amphibolite-facies gneisses into orthopyroxene-bearing,igneous looking charnockites,have been discovered in the early sixties.The fact that some incipient charnockites occur along a network of brittle fractures,together with CO2 remnants preserved in mineral inclusions,had called for the role of fluids during charnockite alteration.The present work presents new observations on fluid inclusions and microtextures of incipient charnockites from type localities in southern India.In addition to CO2-rich fluid inclusions in quartz and feldspar,all of the occurrences have disrupted remnants of concentrated aqueous alkali chloride solutions.CO2 inclusions are more abundant in paragneiss (Kerala) than in orthogneiss (Karnataka/Tamil Nadu).The finding of disrupted brine inclusions in the Kabbal charnockite is a key link between closely associated massive charnockites and Closepet Granite,both of which also share the brine remnants.All of the occurrences studied here have feldspar or feldspar-quartz microvein networks along grain boundaries of recrystallized quartz,feldspar and orthopyroxene.These metasomatic veins again indicate the action of alkali-exchanging fluids (i.e.,saline solutions).Feldspar microveins,which have been found in most “massive” charnockites,along with the CO2-rich fluid inclusions,suggest a commonality of incipient charnockite and massive charnockite,both types differing in intensity of interaction with metasomatizing pore fluids.

关键词： incipient charnockite High-grade crustal metamorphism CO2 Brine metasomatism

Frequency-amplitude behavior in the incipient movement of grains under vibration

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Particuology 2018年第5期16卷 1-9页

作者： Karina A.Valenzuela Aracena Jesica G.Benito Luc Oger Irene Ippolito Rodolfo O.Ufiac Ana M.Vidales INFAP.CONICET Departamento de FfsieaFacultad de Ciencias Fisico Matemdticas y NaturalesUniversidad Nacional de San LuisEjerdto de los Andes 950D5700HHWSan LuisArgentina Institut de Physique de Rennes UMR UR1-CNRS 6251Universite de Rennes 1263Avenue du General LeclercCampus de BeaulieuCS 7420535042 Rennes CedexFrance Universidad de Buenos Aires Facultad de IngenierfaGrupo de Medios PorososPaseo Colon 8501063Buenos AiresArgentina

The onset of the movement of particles placed on a horizontal rough surface subject to a vertical sinusoidal vibration is investigated through tracking experiments,theoretical analysis,and numerical simulations. The frequency of vibration needed to move particles decays exponentially with the amplitude of the oscillatory input.This behavior is explained through a simple mechanism in which a forced damped harmonic oscillator with a spring constant represents all the interactions between the particle and the surface.The numerical results compare well with experimental data,demonstrating that the forces included in the numerical calculations suitably account for the main particle response,even though the complexity of the surface is not fully taken into account.Describing the way in which frequency varies with amplitude could be relevant to technological applications such as cleaning of material surfaces.

关键词： Vibration incipient movement Forced oscillator 3D DEM simulation

IMPACT OF AIR-SEA INTERACTION ON THE GENESIS OF TROPICAL incipient VORTEX OVER SOUTH CHINA SEA： A CASE STUDY

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Journal of Tropical Meteorology 2016年第3期22卷 287-295页

作者：郝赛毛江玉吴国雄 LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

Based on 6-hourly sensible heat flux and latent heat flux from the NCEP Climate Forecast System Reanalysis(CFSR) and circulation data from the Japanese 25-year Reanalysis(JRA-25),the initial developing process of tropical cyclone Mindulle(1005) in 2010 has been diagnosed to reveal the impact of air-sea interaction over the South China Sea(SCS) on the genesis of its incipient vortex.The results show that the incipient vortex first occurred east of the Luzon Island on 0000 UTC 20 August,suggesting that the topographic forcing of the Luzon Island for easterly winds over the western Pacific might be one of the factors responsible for the formation of the incipient vortex.During the formation stage of the incipient vortex,strong southeasterlies over the SCS caused warm water of the middle and eastern SCS to flow toward the Luzon Island due to Ekman transport resulting from wind stress,leading to an increase of the sea surface temperature and sensible heat flux into the atmosphere.Although the anomalous sensible heating favored surface pressure to reduce,it was not conducive to the increase of local vorticity associated with the vortex above the heating area because,according to the atmospheric thermal adaptation theory,the anticyclonic vorticity would be created in the lower troposphere due to the decreased vertical gradient of the sensible heating.However,the ascending motions occurred over the eastern area of the anomalous sensible heating due to the augmentation of the vorticity advection with increasing height,causing water vapor to condense in the middle and upper troposphere.In turn,cyclonic vorticity was generated in the lower troposphere due to the increased vertical gradient of the condensation latent heating,resulting in the formation and further growth of the incipient vortex.Therefore,the vorticity creation due to the condensation heating played a dominant role during the subsequent enhancing stage of the incipient vortex.

关键词： tropical cyclogenesis air-sea interaction incipient vortex sensible heating

Effects of loading transition metal(Mn,Cr,Fe,Cu) oxides on oxygen storage/release properties of CeO2-ZrO2 solid solution

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Journal of Rare Earths 2020年第3期38卷 274-280页

作者： Zhizhe Zhai Dali Cui Yongqi Zhang Yongke Hou Meisheng Cui He Zhang Jianhui Song Hao Wang National Engineering Research Center for Rare Earth Materials GRINM Group Corporation LimitedBeijing 100088China Grirem Advanced Materials Co.Ltd. Beijing 100088China

Cerium zirconium-based(CZ) oxygen storage materials(OSMs) play a crucial role in three-way catalysts(TWCs),while CZ needs to be modified to satisfy more rigorous emission standard.In this study,transition metal(TMs=Mn,Cr,Fe,Cu) oxides modified CZ were prepared by incipient wetness impregnation method to improve the oxygen storage capacity of CZ-based materials.To clearly illustrate the influence of TM oxides,N2 adsorption-desorption,X-ray diffraction(XRD),oxygen storage capacity(OSC),temperature programmed reduction by H2(H2-TPR) and X-ray photoelectron spectroscopy(XPS) were used to characterize the physical and chemical properties of samples.It is found that,all modified CZ have higher OSC,lower reduction temperatures than those of pristine CZ.Interaction between TMOs and CZ take precedence over specific surface to influence OSC.Notably,FeOx/CZ has the highest OSC,which is about 1.9 times that of CZ and it could be attributed to synergistic effect between FeOx and CZ;CuOx/CZ has the lowest reduction temperature which is 168℃lower than that of CZ,and it can be explained by hydrogen spillover effect.

关键词： Transition metals Ceria-Zirconia incipient wetness impregnation OSC

Semi-solid rheocasting of grain refined aluminum alloy 7075

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中国有色金属学会会刊：英文版 2010年第S3期20卷 832-836页

作者： U.A.CURLE G.GOVENDER Materials Science and Manufacturing Council for Sci entific and Industrial Research(South Africa)

Near-net shape rheocasting with the Council for Scientific and Industrial Research Rheo casting system(CSIR-RCS) and a high pressure die casting machine was successfully performed on Al-5Ti-1B grain refined aluminum alloy 7075.Grain refinement levels used were 0.03% Ti,0.13% Ti and 0.29% Ti(mass fraction).Tensile tests reveal that the ultimate tensile strengths,at all levels of grain refinement,are at least 97% of the specified minimum.Elongation at fracture increases with the increase of level of grain refinement although a maximum elongation is only 76% of the required minimum elongation in the case of 0.29% Ti.incipient melting,during solution treatment,of the low melting point multinary eutectic causes porosity in the material and accounts for poor elongation results.0.03% Ti has a coarse eutectic structure forming larger pores while 0.29% Ti has a fine structure forming fine pores in the multinary eutectic.The 0.2% offset yield strengths of all the grain refinement levels are at least equal to or above the specified minimum and a decrease is observed with the increase of grain refinement level.There is a clear reduction in grain size from 0.03% Ti to 0.29% Ti in the as-cast condition.An underlying grain structure develops in the T6 condition material which has an inverse size to the as-cast structure;coarse grained as-cast material results in fine grained T6 condition material after solution heat treatment.The decrease in the offset yield strength as grain refinement increases correlates very strongly with the T6 grain sizes according to a Hall-Petch type relationship.

关键词： CSIR-RCS 7075 Al-5Ti-1B high pressure die casting F condition T6 condition incipient melting

Research on cohesive sediment erosion by flow: An overview

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Science China(Technological Sciences) 2008年第11期51卷 2001-2012页

作者： YongHui Zhu JinYou Lu HongZhi Liao JiaSheng Wang BeiLin Fan ShiMing Yao Changjiang River Scientific Research Institute Changjiang Water Resources Commission Wuhan 430010 China River Management Bureau Changjiang Water Resources Commission Wuhan 430010 China

Erosion of cohesive sediment by flow is a very complicated phenomenon occurring worldwide. Understanding and modeling of the erosion process are important for many issues such as the breaching of embankments, riverbank stability, siltation of harbors and navigation channels, service life of reservoirs, distribution of (heavy metal) pollutants and water quality problems. In the last few decades, numerous studies have been done on the erosion of cohesive sediment by flow. Nevertheless, the factors affecting the erosion resistance of cohesive sediment are still not fully understood and the knowledge of the physics of cohesive sediment erosion is in- adequate, as a result the mathematical modeling of this erosion is far from satis- factory. In this paper an overview of the studies on the erosion resistance, erosion threshold and the erosion rate of cohesive sediment by flow is presented. The outcomes achieved so far from the studies and the existing problems have been analyzed and summarized, based on which recommendations are proposed for future research.

关键词： cohesive sediment erosion erosion resistance incipient motion erosion rate flow

Review: the charnockite problem, a twenty first century perspective

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Natural Science 2010年第4期2卷 402-408页

作者： Samarendra Bhattacharya 不详

Beginning of the twentieth century was marked by coinage of a new rock name, Charnockite, first described as a hypersthene-bearing granite from Southern India. Since then charnockites have been described from most of the conti-nents and mostly restricted to high-grade belts. Later half of the last century saw a lively debate over an igneous versus metamorphic origin. However, two factors acted as deterrents for the resolution of the debate. First, charnockites and associated rocks occur in a variety of different structural setting and display diverse field rela-tions, attesting to possible different mode of origin. Second and possibly more important is the lack of consensus on the nomenclature of charnockites and associated rocks and this is commonly linked with the metamorphic versus magmatic perspective. Scanning the literature of this period makes one believe that both metamorphic and magmatic hypotheses are valid, but applicable to different field setting only. Before critically evaluating individual cases, it is imperative that a uniform approach in nomenclature should be agreed upon. It is proposed that name charnockite be adopted for any quartzofeldspathic rock with orthopyroxene, irrespective of its mode of occurrence, struc-tural setting and mode of origin. The associated more mafic varieties, be better described as mafic granulite, rather than basic charnockite. For the patchy charnockites of east Gondwana (including parts of Peninsular India, Sri Lanka and Antarctica), metamorphic transformation from amphibolite facies gneiss, by two different mechanisms: CO2 ingress from deep level, and drop in fluid pressure, has been proposed. However, all such patchy occurrence is not amenable to explanation by metamorphic trans- formation. In some instances, migmatisation of older charnockitic rocks is evident. Also pro- gressive charnockitisation relating patchy char-nockite to banded variety could be argued against on two counts: grain-size relation and time-relation. Larger bodies or bands have been explained a

关键词： incipient Growth Progressive Charnockitisation Plutonic Charnockite Partial Melting Plutonic Metamorphism

Thickness, Distribution and Quality Assessment of Gopalganj-Madaripur Peat Deposits: A Case Study of Potential Economic Opportunities in Mid-Eastern Low-Lying Bangladesh

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International Journal of Geosciences 2014年第9期5卷 943-955页

作者： Mrinmoy Kumar Maitra Md. Ashraful Islam Md. Al Mamun Department of Geological Sciences University of Canterbury Christchurch New Zealand Department of Geology University of Dhaka Dhaka Bangladesh Padma Mining & Energy Corporation Limited Dhaka Bangladesh

The present research work illustrates the extent, distribution and a generalized quality assessment of southern low-lying peat deposits in Madaripur and part of Gopalganj district that covers approximately 17,000 hectare areas. Based on the survey of 800 boreholes, drilled in this region at different times by several government and non-government organizations for the purposes of peat exploration and hydrogeological investigation, reveals that the study area is composed of a considerable amount of peat deposits in various localities among which the deposits at Baghia-Chanda beel in Madaripur and Gopalganj districts are the most remarkable. The average peat thickness (in-situ condition), studied during field investigation, is 6.5 feet for the upper peat deposits, overlying with an average of 3.5 feet of alluvium cover, followed by the lower peat layer of about 3 feet thick that begins at an average depth of 8 feet and separated by a thin bluish grey silty clay sediments from the upper one. The lower part of the study area, locally known as beels, is the most prospective region for peat, whereas the western part is less potential either having no peat intersection or minimal peat thickness. The overburden covers, on the other hand are inversely correlated with the peat thicknesses, i.e., thick overburden tend to correlate with thin peat deposits and the thickest peat intersections have no or minimal overburden. Due to the variation in bulk density and peat depth, this Holocene peat has an average of 59.10% carbon stock. Nitrogen levels, more than 3%, indicate that the peat developed from the decomposition of reeds, sedges, bushes and trunks of trees (higher in nitrogen) rather than either moss or grass (lower in nitrogen). Higher sulphur content (about 2.7%) reflected the influence of brackish environments where the formation of FeS2 took place in the roots of existing vegetation. The calorific values, about 1308.8 k-cal/kg (after 20% moisture reduction), suggest that the Gopalganj-Madaripur peat is a low grade fue

关键词： Bengal Basin Depression incipient Peat Proximate Analysis