材料期刊网

Mn-Series Low-Carbon Air-Cooled Bainitic Steel Containing Niobium of 0.02%

FENG Chun , FANG Hong-sheng

钢铁研究学报(英文版)

A new hot-rolled low carbon air-cooling bainitic steel containing 0.02%Nb has been developed based on alloying design of the grain boundary allotriomorphic ferrite (FGBA)/ granular bainite (BG) duplex steel.The as-rolled microstructure and mechanical properties of 0.02%Nb bainitic steel were investigated by tensile test, X-ray diffraction(XRD),Optical Microscopy (OM), scanning electron microscopy (SEM) ,and Transmission electron microscopy(TEM). The results show that (1) The addition of 0.02% niobium improves the strength obviously without sacrificing toughness of the FGBA/BG steel. Compared with Non-Nb FGBA/ BG steel, 0.02% Nb increases the tensile strength and yield strength about 20% (From 780Mpa to 937Mpa)and 17%(From 557Mpa to 650Mpa) respectively, remaining 18% elongation and 83J Akv. (2) Small addition of Nb(0.02%) not only refines the allotriomorphic ferrite grain but also promotes the nucleation of intragranular ferrite, both of which in turn contribute to the refinement of granular bainite cluster including its ferrite platelets and M-A islands. Compared with Non-Nb steel, the volume fraction of M-A island in 0.02%Nb steel increases from 21% to 31%, and the average size of M-A island decreases from 1.2μm to 0.95um.(3)There is hardly any Nb(C,N) has been observed in 0.02%Nb steel. It is suggested that the strengthening effect of 0.02%Nb can be mainly attributed to the influence of the segregation of Nb to γ/α phase boundaries(solute drag-like effect) on the phase transformation rather than the precipitation strengthening of Nb(C,N).

关键词: Low carbon air cooling bainitic steel;Small addition of Nb;Microstructure;Mechanical properties

Preface to Special Issue on Photocatalysis for celebrating the 20th anniversary of Professor Jimmy C. Yu’s return to Hong Kong and leading photocatalytic research there

催化学报 doi:10.1016/S1872-2067(15)61006-3

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1998 COMPREHENSIVE TABLE OF CONTENTS

中国腐蚀与防护学报

N。1Atmospheric Corrosivlty for Steels………………………………………………… .LIANG Caideng HO[I i。-tat（6）Caustic Stress Corrosion Cr。king of Alloy 800 Part 2.The Effect of Thiosul执e……………………………………… KONG De-sheng YANG Wu ZHAO Guo-zheng HUANG De.ltL。ZHANG Yu。。he CHEN She。g-bac（13）SERS slid E16CttOCh6iniC81 Stlldy Of Illhibit1Oli M6ch＆tllsth Of ThlollY68 Oil ITOll ID H....

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New criteria of glass forming ability, thermal stability and characteristic temperatures for various bulk metallic glass systems

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

Six mathematical criteria used for quantitatively measuring their glass forming ability, thermal stability and characteristic temperatures (temperature of glass transition T-g, crystallization onset T-x and liquidus T-l) of various bulk metallic glasses (BMGs) have been proposed in this article. It is found that the criteria are suitable for evaluating these quantities for BMGs. The estimated results are better than those calculated by Fang et al.'s models and Lu et al.'s gamma criterion, but our analyses indicate that these criteria, defined by the data (Pauling electronegativity xi, atomic radius ri, electron concentration ni and melting temperature T-mi) easily found in literatures, still need to be further refined in future research for shortcomings of the parameters. (C) 2007 Elsevier B.V. All rights reserved.

关键词: bulk metallic glasses;glass forming ability;thermal stability;supercooled liquid regions;mechanical-properties;amorphous-alloys;transition temperature;bond parameters;strength;binary;widths;ag

Hardness of T-carbon: Density functional theory calculations

Physical Review B

We reconsider and interpret the mechanical properties of the recently proposed allotrope of carbon, T-carbon [Sheng et al., Phys. Rev. Lett. 106, 155703 (2011)], using density functional theory in combination with different empirical hardness models. In contrast with the early estimation based on Gao et al.'s model, which attributes to T-carbon a high Vickers hardness of 61 GPa comparable to that of superhard cubic boron nitride (c-BN), we find that T-carbon is not a superhard material, since its Vickers hardness does not exceed 10 GPa. Besides providing clear evidence for the absence of superhardness in T-carbon, we discuss the physical reasons behind the failure of Gao et al.'s and Simunek and Vackar's (SV) models in predicting the hardness of T-carbon, residing in their improper treatment of the highly anisotropic distribution of quasi-sp(3)-like C-C hybrids. A possible remedy for the Gao et al. and SV models based on the concept of the superatom is suggested, which indeed yields a Vickers hardness of about 8 GPa.

关键词: superhard rhenium diboride;elastic-constants;ambient-pressure;metal;borides;crystals;diamond;search;boron

ATOMIC FORCE MICROSCOPY OBSERVATION OF MAGNETRON SPUTTERED ALUMINUM-SILICON ALLOY FILMS

金属学报(英文版)

粒裕希停桑谩。疲希遥茫拧。停桑茫遥希樱茫希校佟。希拢樱牛遥郑粒裕桑希巍。希啤。停粒牵危牛裕遥希巍。樱校眨裕裕牛遥牛摹。粒蹋眨停桑危眨停樱桑蹋桑茫希巍。粒蹋蹋希佟。疲桑蹋停?##2##3##4##5ATOMICFORCEMICROSCOPYOBSERVATIONOFMAGNETRONSPUTTEREDALUMINUM-SILICONALLOYFILMSJ.W.Wu,J.H.FangandZ.H.Lu(NationalLaboratoryofMoleculeandBiomoleculeElectronics,SoutheastUniversity,Nanjing210096,ChinaManuscriptreceived27October1995)Abstrcat:Twodifferentsurfacemorphologycharacteristicsofmagnetronsputteredaluminumsilicon(Al-Si)alloyfilmsdepositedat0and200℃wereobservedbyatomicforcemicroscopy(AFM).Oneisirregularlyshapedgrainsputtogtheronaplane.TheotherisirregularlyshapedgrainsPiledupinspace.Nanometer-sizedparticleswithheightsfrom1.6to2.9nmwerefirstobserved.Onthebasisoftheseobservationsthegrowthmechanismofmagnetronsputteredfilmsisdiscussed.Keywords:magnetronsputtering,Al-Sialloy,surfacemorphology,atomicforcemicroscopy,filmgrowthmechanism1.IntroductionTheuseofaluminumalloys[1,2],inparticularAl-Si,isacommonfeatureinmanysinglelevelandmultilevelinterconnectionschemesadoptedinthemanufactureofmicroelectronicdevicesbecauseofseveraldesirableproperties.TheAl-Sigrainmorphology(size.geometryanddistributionofgrainsisassociatedwithstepcoverage[3],electromigration[4]andinterconnectsresistivity[5]etc..Thus,characterizationofAl-Sialloysurfacemorphologyisveryimportant,especiallywhenintegratedintensityincreasesandlinewidthsof0.3to0.5μmbecomecommon.Inthepasttwentyyears,theAl-Sialloysurfacemorphologywhichaffectsthereliabilityofmicroelectronicdeviceshasbeenwidelyinvestigatedbyscanningelectronmicroscopy(SEM),transmissionelectronmicroscopy(TEM)etc.[5-7].However,SEMandTEMhavetheirlimitationorinconvenience,forexample,theverticalresolutionofSEMisnothighandTEMneedscomplexsamplepreparation.Recently,anewgrainboundaryetchingmethodwasproposed￣[8]whichalsoneedstroublesomechemicaletching.Atomicforcemicroscopy(AFM),sinceitsemerging,hasbecomemoreandmoreusefulinphysics,chemistry,materialsscienceandsurfacescience,becauseofitshighresolution,easeofsamplepreparationandrealsurfacetopography.Recently,discussion[9,10]waspresentedonhowAFMwillplayaroleinsemiconductorindustry.Asaresponsetothisdiscussion,weusedAFMtoinvestigateAl-SialloysurfacemorphologyandhaveobtainedsomeresultswhichcannotberevealedbySEMorTEM.ThisindicatesthatAFMisagoodcharacterizationtoolinsemiconductorindustry.2.SamplePreparationInourexperiments,aluminumwith30ppmsiliconwassputteredonsiliconsubstrateinbatchdepositionmodeAllthreefilmswiththicknessof1.6μmweredepositedusinganargonsputteringpressureof4.2×10￣-3Pa.TheotherdepositionparametersaredescribedinTable1.Thesubstratewascleanedusingstandardpremetallizationcleaningtechniquespriortofilmdeposition.3.ExperimentalResultsandDiscussionTheAFMmeasurementswereperformedonacommercialsystem(NanoscopeIII,DigitalInstruments,SantaBarbara).Thetipismadeofmicrofabricatedsiliconnitride(Si_3N_4)Itisattachedtoa200μmcantileverwithaforceconstantofabout0.12N/m.Beforethesurfaceofsamplewasexamined.agoodtipwithananometer-sizedprotrusionatitsendwasselectedbeforehand,whichcanbeobtainedbyimagingtheatomicstructureofmicasubstrateandagoldgrid.AtypicaloperatingforcebetweenthetipandAl-Sisamplesurfaceisoftheorderof10￣-8Nandallimagesweretakenatroomtemperatureinair.AtypicaltopographicviewoftheAl-SifilmsisshowninFig.1(allimagescansizeis5by5μma,bandcarerespectivelyforsample1,2,and3).FromFig.la,itcanbeseenthatirregularlyshapedgrainstiltinginvaryingdegreespileupinspace,andgroovesamongtheirregularlyshapedgrainsaredifficulttodecideatacertainarea(wedefineitascharacteristicA).Toourknowledge,onreportsonthesurfacemorphologyhavebeenpresentedbefore.InFig1b,however,irregularlyshapedgrainsassembleonaPlaneandgroovesamongtheirregularlyshapedgrainsareeasytodecide(wedefineitascharacteristicB),whichisinagreementwithmanypreviousreports[5-7].InFig.1c,bothcharacteristicA(arrowA)andcharacteristicB(arrowB)wereobserved.IndoingAFMexperiments,weselectedfivedifferentscanareastobeimagedforeachsampleandfoundthatallimagesofeachsamplearerespectivelysimilartoFig.1a,bandc.Also,wenotedthatthesurfaceofinFig.1a.WethinkthatdepositionparameterswillinfluenceAl-Sisurfacemorphology,andthetiltedgrainsmaybesusceptibletomicrocracking.Byreducingthescansizeareato2by2μm(Fig.2aandb).Weobtainedmanyidenticalresultsasdescribedabove,suchasirregularlyshapedgrainsetc.Forthefirsttime,wefoundnanometersizedparticlesonirregularlyshapedgrainsurfacewhichcannotberevealedbySEMbecausethediameterofthesenanoparticlesisabout10nmandtheheightofthesenanoparticlesisintherangeof1.6to2.9nm.Inimaging,wenotedthatrotatingthescandirectionandchangingthescanfrequencydidnotaffectthestructureofthesegrainsasshowninFig.2aandb,rulingoutthepossibilitythatscanninginfluencedtheshapeoftheseparticlesorcausedsomesimilarimagingartifacts.Also,wenotedthatthenanoparticleswerenotobservedontheslopesofthegrooves(Fig.2aandb).Thisphenomenoncanbeexplainedasfollows:thepotentialenergyattheslopeislargerthanthatelsewhere,sotheparticlesseemmorelikelytobedepositedontheseareaswithlowerpotentialenergy.Fig.2c,scansize250by250nm,isazoomtopographicimage(whiteoutlineinb).Itshowsunevendistributionofthenanoparticles.Andtheheightdifferenceofthenanoparticlesindicatesdifferentgrowingspeed.Wethinkbasedonthemorphologyofnanoparticles,thattheheightdifferenceandunevendistributionofthesenanoparticlesshowdifferentgrowingadvantageandindicatethatatomshaveenoughenergytomovetoasuitablegrowingspot.Theenergymaybefromthefollowingsources:surfacetemperaturefluctuation,stressdifferenceorcollisionbetweenhighspeedsputteredatoms.Thesenanoparticlesgoongrowingandformmanyirregularlyshapedgrains.AndtheseirregularlyshapedgrainsfurtherconnecteachotheraccordingtocharacteristicAorB,finallyformingtheAl-Sisurfacemorphology.4.ConclusionWecandrawthefollowingconclusionsfromtheabove.First,theexperimentalresultsshowedthatAFMisapowerfultooltoinvestigatethedetailsofAl-Sisurfacemorphologywhichcangreatlyenrichourknowledgeofthefilmgrowthmechanism.Second,depositionconditionsplayanimportantroleindeterminingtheAl-Sisurfacemorphology.Third,thetwoAl-Sisurfacemorphologycharacteristicsarethatirregularlyshapedgrainsassembleonaplaneandirregularlyshapedgrainstiltinginvaryingdegreespileupinspace.Fourth,forthefirsttime,nanoparticleswereobservedonirregularlyshapedgrainsurfacewhichsuggestedthatthefilmgrowthmechanismwasbyinhomogeneousnucleation.Acknowledgements-BeneficialdiscussionswereheldwithDr.ZhenandMr.Zhu.ThisworkwaspartiallysupportedbytheNationalNaturalScienceFoundationofChina.RFFERENCES｜｜1D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)127.2D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)131.3D.pramanikandA.N.Saxena,SolidStateTechnol.33(1990)73.4S.S.IyerandC.Y.Worg,J.Appl.phys.57(1985)4594.5J.F.Smith,SolidStateTechnol.27(1984)135.6D.GerthandD.Katzer,ThinSolidFilm208(1992)67.7R.J.WilsonandB.L.Weiss,ThinSolidFilm207(1991)291.8E.G.Solley,J.H.Linn,R.W.BelcherandM.G.Shlepr,SolidStateTechnol33(1990)409I.SmithandRHowland,SolidStateTechnol.33(1990)53.10L.Peters,SemiconductorInternational16(1993)62.##61D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)127.2D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)131.3D.pramanikandA.N.Saxena,SolidStateTechnol.33(1990)73.4S.S.IyerandC.Y.Worg,J.Appl.phys.57(1985)4594.5J.F.Smith,SolidStateTechnol.27(1984)135.6D.GerthandD.Katzer,ThinSolidFilm208(1992)67.7R.J.WilsonandB.L.Weiss,ThinSolidFilm207(1991)291.8E.G.Solley,J.H.Linn,R.W.BelcherandM.G.Shlepr,SolidStateTechnol33(1990)409I.SmithandRHowland,SolidStateTechnol.33(1990)53.10L.Peters,SemiconductorInternational16(1993)62.##A##BATOMIC FORCE MICROSCOPY OBSERVATION OF MAGNETRON SPUTTERED ALUMINUM-SILICON ALLOY FILMS$$$$J.W.Wu,J.H. Fang and Z.H.Lu (National Laboratory of Molecule and Biomolecule Electronics,Southeast University,Nanjing 210096, China Manuscript received 27 October 1995)Abstrcat:Two different surface morphology characteristics of magnetron sputtered aluminumsilicon(Al-Si)alloy films deposited at 0 and 200℃ were observed by atomic force microscopy(AFM).One is irregularly shaped grains put togther on a plane.The other is irregularly shaped grains Piled up in space. Nanometer-sized particles with heights from 1.6 to 2.9 nm were first observed. On the basis of these observations the growth mechanism of magnetron sputtered films is discussed.

关键词: :magnetron sputtering , null , null , null , null