工程热物理学报
根据《吴仲华奖励基金章程》（吴奖[2008]01号），经各高等院校、中国工程热物理学会和中国科学院工程热物理研究所认真评选和推荐，吴仲华奖励基金理事会评审并确定授予青年学者戴巍、罗坤、唐桂华“吴仲华优秀青年学者奖”，授予程雪涛等10位同学“吴仲华优秀学生奖”。
关键词:
基金
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奖励
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评选
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获奖者
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中国科学院
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青年学者
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物理研究所
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高等院校
王璐
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史庆南
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起华荣
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赵启淞
,
姜义
机械工程材料
向Zn-35％Sn合金中加入不同含量的镁元素,研究了镁含量对该合金显微组织和力学性能的影响,并分析了拉伸断口形貌.结果表明:加入微量的镁元素就会对Zn-35％Sn合金的显微组织和力学性能产生显著影响(伸长率急剧下降);加入到合金中的镁元素,一部分固溶于富锌的η相中,使该相原子沿垂直于密排面方向堆垛,形成棒状组织;另一部分与锡反应生成Mg2Sn,Mg2Sn作为异质晶核促进脆锡相(γ-Sn)的形核生长,且阻碍脆锡相向白锡相(β-Sn)的同素异构转变,使脆性组织保留下来;随着镁含量的增加,η相棒状晶粒尺寸增大,取向性逐渐明显,断裂解理面变大,塑韧性急剧下降.
关键词:
锌锡合金
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镁
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显微组织
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力学性能
金属学报(英文版)
桑危郑牛樱裕桑牵粒裕桑希巍。希啤。龋伲模遥希牵牛巍。桑危模眨茫牛摹。模眨茫裕桑蹋拧。拢遥桑裕裕蹋拧。裕遥粒危樱桑裕桑希巍。桑巍。罚保罚怠。粒蹋眨停桑危眨汀。粒蹋蹋希?##2##3##4##5INVESTIGATIONOFHYDROGENINDUCEDDUCTILEBRITTLETRANSITIONIN7175ALUMINUMALLOY$R.G.Seng:B.JZhong,MG.ZengandP.Geng(DepartmentofMaterialsScierce,ScienceCollege,NorthearsternUniveisity,Shenyang110006,ChinaMaruscriptreceived4September1995inrevisedform20April1996)Abstrac:Effectsofhydrogenonthemechanicalpropertiesofdifferentlyaged7175aluminumalloyswereinvestigatedbyusingcathodicH-permeation,slowstrainratetensionandsoon.Theresultsindicatethatboththeyieldstressandthepercentagereductionofareadecreasewithincreasinghydrogenchargingtime,andthedegreeofreductiondecreasesasagingtimeincreasesforthesamehydrogenchargingtime.Keywords:hydrogeninducedductile-brittletransition,7175aluminumalloy,mechanicalproperty,cathodicH-permeation1.IntroductionForalongtimehydrogenembrittlementproblemwasthoughttobeabsentinhighstrengthaluminiumalloybecausethesolutiondegreeofhydrogeninaluminumatcommontemperatureandpressureisverysmall.However,hydrogenembrittlementphenomenonwasfoundinaluminumalloyduringtheinvestigationofstresscorrosionandcorrosionfatigue[1-5].Therehavebeenonlyafewreportsofhydrogeninducedsofteningandhardening.Inthispaper,theeffectsofhydrogenonmechanicalpropertiesof7175aluminumalloywereinvestigatedbyusingcathodicalchargingwithhydrogenandslowtensiontests.2.ExperimentalProcedureTheexperimentalmaterialwas7175aluminumalloyforgingintheformofa43mminthicknessandwithcomposition(wt%).5.41Zn,2.54Mg.1.49Cu,0.22Cr,0.1Mn.0.1Ti,0.16Fe.0.11Si,balancedbyA1.Alloyplateof1.5mminthicknesswasobtainedbyhot(465℃)andtoldrollingto83%reductioninthickness.Thelongaxisofhydrogenchargedspecimensisalongtherollingdirection.Allspecimensweresolidsolutionedat480℃for70min,followedtyimmediatequenchinginwaterandthenagedat140℃for6h(A),16h(B)and98h(C).Thetreatmentof6hiscorrespondingtotheunderagedstate.16hthefirstpeak-agedstateand98hthesecondpeak-agedstate.Thespecimenswerepolishedsuccessivelyusingemerypaperbeforehydrogencharging.Thetensilespecimenswerecathodicallychargedina2NH_2SO_4solutionwithasmallamountofAs_2O_3forpromotinghydrogenabsorption,andwithacurrentdensityof20±1mA/cm￣2atroomtemperature.ThehydrogencontentanalysiswascarriedoutonanLT-1Amodelionmassmicroprobeafterthesputteringdepthreached8nm.Theioncurrentsofhydrogenandaluminuminvariousagedstateswererecordedunderthesamecondition.ThetensiletestswereperformedonanAG-10TAmodeltestmachinewhichwascontrolledbycomputer.3.ExperimentalResultsTheratioofioncurrentstrengthofhydrogentoaluminumisrelatedtohydrogenconcentrationinhydrogenchargedspecimen.TheresultswereshowninTable1Thehydrogencontentincreaseswiththeincreaseincharingtime.Ofthethreeagedstates,theunderagedspecimenhasthehighesthydrogencontent.Theratioofyieldstrengthofhydrogenchargedandunchargedspecimenschangeswithhydrogenchargingtime,asshowninFig.1Itcanbeseenthattheyieldstrengthofhydrogenchargedspecimendecreasewithincreasinghydrogenchargingtime.Atthesamechargingtime,theyieldstressdecreasestheleastinthesecondpeak-agedstate,anddecreasesthemostintheunderagedstate.Itindicatesthattheunderagedspecimenismostsensitivetohydrogeninducedsoftening,whichisconsistentwiththeresultsofanotherhighstrengthaluminumalloy[6].TherelativechangesoftheradioofreductionofareawithhydrogenchargingtimearesummarizedinFig.2,whereΨ￣0andΨ￣Harethepercentagereductionofareaofthesamplewithoutandwithhydrogenchargingrespectively.Theradioofreductionofareareduceswhenhydrogenchargingtimeincreases,andthedecreasingdegreeofreductionofareaincreaseswithincreasingagingtime,ie,,theunderagedstateisthemostsensitivetohydrogenembrittlement.4.DiscussionItisknownfromtheresultsabovethatcathodicalchargingwithhydrogenleadstotheobviousdecreaseinthetensilestrengthandplasticityThisisbecausealargeamountofsolidsolutionhydrogenentersthespecimenintheprocessofhydrogenchargingSolidsolutionhydrogenisliabletoenterthecentreofdislocationundertheactionofdislocationtrap,henceraisingthemovabilityofdislocation.Thereforethedislocationsinhydrogenchargedspecimenmoveeasierthaninunchargedspecimen.soresultinginthereductionofyieldstrength[7].Whendislocationstartstomove,thecrystallatticeresistance(P-Nforce)whichitmustovercomeisgivenby:whereμismodulusofshear,visPoissonratio,aisspanofslipplane,bisatomspanofslipdirection.Moreover.theotherresistanceofdislocationmotionmayarisefromtheelasticinteractionofdislocation,theactionwithtreedislocationandetc.,itcanbeexpressedasfollows:whereαisconstant,XisdislocationspanSotheresistanceofdislocationmotioncanbewrittenasfollows:Becausehydrogenatomsreducetheatombondingstrengthafterhydrogencharging,shearmodulusμdecreasesandresultsinthereductionoff,therebytheyieldstressdecreases.Asthecentreofdislocationistheseriousdistortionzoneoflattice.thestresscanberelaxedafterhydrogenatomstuffing,andthesystemenergydecreases.Thusthecentreofdislocationisastrongtrapofhydrogen[8].Therefore,amovabledislocationcaptureshydrogenandmigratestograinboundaries.phaseboundariesorsurfaceofthespecimen,promotingthecrackiesformationandgrowth,thuscausingthelossofplasticity.Sincethelocalenrichmentofhydrogenisrealizedbydislocationtransporting(inthestageofdeformation),thelargerthereductionofyieldstress.theearlierarehydrogenatomstransportedtotheplaceofenrichment.Inaddition,thedamageofatombondingstrengthinducedbyhydrogenmakesthefracturestressdecrease[9]:whereCHishydrogenconcentration.σ_thisfracturestrengthbeforehydrogenchargingandisfracturestrengthafterhydrogencharging.Eq.(4)showsthatthematerialsmaybefracturedatalowerstraini.e.,brittlefractureoccurs.5.Conclusions(1)Hydrogencontentofdifferentlyagedspecimensincreaseswithincreasinghydrogenchargingtimethecapabilityofthealloytoabsorbhydrogeninunderagedstateisthestrongest.(2)Theyieldstressaswellasthepercentagereductionofareaof7175aluminumalloydecreaseashydrogenchargingtimeincreasesundervariousagedstates.(3)Underagedstateismostsensitivetohydrogeninducedsofteningandhardening.(4)Anexplanationwasofferedforthephenomenonofhydrogeninducedsofteninginthestageofdeformation,andhardeninginthestageoffracture.REFERENCES｜｜1G.KKock,Corrosion35(1979)73.2M.K.TsengandH.LMarcus,Scr.Metall.15(1981)427.3PSFao.M.GaoandR.P.Wei,Scr.Metall.19(1985)265.4R.G.SongandM.K.TsengJ.NortheasternUniversity15(1994)5(inChinese).5R.K.Viswanadham,T.S.sunandJ.A.S.Green,Metall.Trans.11A(1980)85.6J.Liu,M.KTsengandB.R.Liu.NonferrousMiningandMetallrgy5(1989)33(inChinese).7LChen,WXChen,ZHLiuandZ.Q.Hu,InFrocofthe1stNationalConfonAl-LiAlloys(Sheryang.China,1991)p.328(inChinese).8Z.HLiuL.ChenW.XChenY.X.ShaoandZ.Q.Hu,InProc.ofthe1stNationalConfonAl-LiAlloys(Shenyang,China,1991)p.334(inChinese).9R.A.OrianiandF.H.Josephic,ActaMetall.22(1974)1065.##61G.KKock,Corrosion35(1979)73.2M.K.TsengandH.LMarcus,Scr.Metall.15(1981)427.3PSFao.M.GaoandR.P.Wei,Scr.Metall.19(1985)265.4R.G.SongandM.K.TsengJ.NortheasternUniversity15(1994)5(inChinese).5R.K.Viswanadham,T.S.sunandJ.A.S.Green,Metall.Trans.11A(1980)85.6J.Liu,M.KTsengandB.R.Liu.NonferrousMiningandMetallrgy5(1989)33(inChinese).7LChen,WXChen,ZHLiuandZ.Q.Hu,InFrocofthe1stNationalConfonAl-LiAlloys(Sheryang.China,1991)p.328(inChinese).8Z.HLiuL.ChenW.XChenY.X.ShaoandZ.Q.Hu,InProc.ofthe1stNationalConfonAl-LiAlloys(Shenyang,China,1991)p.334(inChinese).9R.A.OrianiandF.H.Josephic,ActaMetall.22(1974)1065.##A##BINVESTIGATION OF HYDROGEN INDUCED DUCTILE BRITTLE TRANSITION IN 7175 ALUMINUM ALLOY$$$$R.G.Seng: B.J Zhong, MG. Zeng and P. Geng(Department of Materials Scierce, Science College,Northearstern Univeisity, Shenyang 110006, China Maruscript received 4 September 1995 in revised form 20 April 1996)Abstrac:Effects of hydrogen on the mechanical properties of differently aged 7175 aluminum alloys were investigated by using cathodic H-permeation, slow strain rate tension and so on. The results indicate that both the yield stress and the percentage reduction of area decrease with increasing hydrogen charging time, and the degree of reduction decreases as aging time increases for the same hydrogen charging time.
关键词:
:hydrogen induced ductile-brittle transition
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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
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金属学报(英文版)
茫遥伲樱裕粒蹋蹋桑冢粒裕桑希巍。希啤。疲錩(38)Ni_(39)Si_(10)B_(13) METALLIC GLASS UNDER HELIUM ION IRRADIATION##2##3##4##5CRYSTALLIZATIONOFFe_(38)Ni_(39)Si_(10)B_(13)METALLICGLASSUNDERHELIUMIONIRRADIATION$YANGQifa(ChinaInstituteofAtomicEnergy,Beijing)ZHANGGuoguang;SHENWanshui(UniversityofScienceandTechnologyBeijing)Manuscriptreceived20February1995ThecrystallizationfeaturesofFe38Hi39Si10B13metallicglassunder100keVand6μA/cm2heliumionirradiationwithdifferentdosesarereported.ItisfoundthattheFe38Ni39Si10B13metallicglasscrystallizedundertheheliumionirradiationatthetemperaturelowerthantheordinarythermalcrystallizationtemperature.ThepreferentialprecipitationphaseisFeSi,andfollowedbytheeutecticphaseα-Fe.Thecriticaldosefortheformationofheliumbubblesinthematerialisaround5x10￣16/cm2.Thesensitivityofcrystallizationduetothetemperaturerisingunderheliumionirradiationandthemechanismofthesequenceofprecipitatedphasearebrieflydiscussed.Keywords:Fe38Ni39Si10B13,metallicglass,crystallization,helium,ionirradiationTheblisteringorflakingoffirstwallmaterialsinducedbyheliumionbombardment,whichisrelevanttothefirstwallsurfaceerosionandplasmacontamination,isacriticalproblemtobeconsideredinfusionengineering.Becauseofthefavourablyphysical,chemicalandotherproperties,especially,thebetterresistanceofblistering,metallicglassesareexpectedtobeapromisingcandidatematerialforthefirstwall.TyagiandNanderkarstudiedsystematicallytheblisteringphenomenaofsomemetallicglassmaterialsunderheliumionandprotonbombardmentwithvariousionenergy,ioncurrentdensityanddose,andfoundthecriticaldoseforblisteringofthesematerials[1-3].However,itisverysuspiciousthatmetallicglasseswillcrystallizeunderheliumionirradiationtolosetheiramorphouscharacter,whichwilldeterioratetheirproperties.GusevaandGordeevareportedthatFe40Ni40B20metallicglassbombardedbyheliumionwithenergyof40keVandionbeamcurrentdensitiesof5-40μA/cm2partiallycrystallizedbelowitsordinarythermalcrystallizationtemperature[4].ByusingXRDexamination,itwasfoundthatα-FeandM3B,M2BandMBwereprecipitated(whereM=FeandNi)underheliumionbombardmentwith5μA/cm2and100μA/cm2ioncurrentdensitiesrespectively.Nevertheless,TyagiandNanderkarfoundthatsomemetallicglassescrystallizedandsomedidnotundersameirradiatedparameters[1-3].Consequently,itisnecessarytoinvestigatetheirradiation-assisted-crystallizationfeatureofmetallicglassesbyheliumionirradiationfortheirapplicationinfusionengineering.Inpresentexperiment,thecrystallizationfeatureofFe38Ni39Si10B13metallicglassunderheliumionirradiationwithenergy100keVandvariousdosesintherangeof5×1016/cm2to1×1018/cm2,andthedistributionofheliumbubblesinmaterialaremeasuredbyusingtransmissionelectronmicroscope(TEM)andX-raydiffraction(XRD).1.ExperimentalApproachTheas-receivedFe-Ni-Si-Bmetallicglassribbonswith10mminwidthand0.2mminthicknessweresuppliedbyBeijingInstituteofMetallurgy.Thenominalcomposition(wt%)ofthematerialisNi47.37,Fe43.91,Si5.81andB2.91fromthechemicalanalysisandthecalculatedconstituentisFe38Ni39Si10B13.TheX-raydiffractogramofas-receivedmaterialdemonstratedthattheas-receivedmaterialhasagoodamoophouscharacter.Thetheimalcrystallizationprocessoftheas-receivedmaterialwastestedbydifferentialthermalanalysis(DTA).Theordinarythermalcrystallizationtemperaturewasdeterminedtobeabout490℃.Rectangularsampleswithanareaof1×2cmanddiscsampleswith3mmindiameterwereemployedrespectivelyforXRDandTEMexperiments.ThesamplesforXRDweremechanicallypolishedtomirrorsurfaee.Ontheotherhand,formakingTEMsamples,thepiecescutfromtheribbonwerethinnedto30μmthicknessfirst,thenpunchedout3mmdiscs,electrothinnedinamixedsolutionof10%perchloricacidand90%ethanolandfinally,thediscswereionmilledtoextendthethinarea.HeliumionirradiationofsampleswascarriedoutonTS51-200/ZKionimplanterinChinaInstituteofAtomicEnergy.ThesampleswerefixedonacopperholderwhichwascooledbyF-113coolant.Thevacuumintargetwasbetterthan3×10-3Paandthescanningareaofionbeamwasabout3×7cm.Thetemperatureridingofthesamplescausedbyionbeambombardmentwasmeasuredbythermalcouple.Undertheirradiationparametersofionbeamenergy100keVandionbeamcurrentdensity6μA/cm2,thetemperaturerisingofsampleswaslowerthan200℃.Theiondosesofimplantedsampleswerechosenfrom5×10￣16/cm2to1×10￣18/cm2inpresentexperiment.AJEOL-100CXTEMoperatedat100kVwasused.Thecalculatedmeanprojectrangeandrangestragghngofheliumionwithenergy100keVinthematerialwere306.9nmand85.5nmrespectively,whichwassimulatedbycodeTRIM86.2.Results2.1CrystallizationunderionirradiationTheselectedareadiffraction(SAD)patternsofun-irradiatedandirradiatedsamplesareshowninFig.l.Fortheun-irradiatedsample,thepatterniscomposedoftwoconcentricringswhichexhibitatypicalamorphousdiffractionfeature(Fig.la).Ontheotherhand,forirradiatedsamples,agroupofnewconcentricringsappearsonthebaseofamorphousdiffractionrings,whichmeanstheoccurrenceofpartialcrystallizationandtheformationofsomenewprecipitationphasesinoriginalamorphousmaterialsbyionirradiation.Withtheincreaseofiondose,theinitialamorpohousdiffractionringsbecomefainterandtheintensitiesofdiffractionringsprodueedbyprecipitatesdevelopehigher.Itisexpectedthatthecrystallizationinsamplesincreaseswiththeincreaseiniondose.Moreover,iftheiondoseislowerthan5×10￣17/cm2,thepatternsshowtypicalpolycrystallinediffractionfeaturewithrandomorientationandveryfinegrains(Figs.lbandlc),butfor1×10￣18/cm2iondose,somebrightspotsarise(Fig.ld),thismeansthatsomerelativelargegrainsformedinsampleunderirradiation.FromtheX-raydiffractogramofthesampleirradiatedbyheliumiontodoseof5×10￣17/cm2,thediffractionpoaksarestillamorpohousfeatureandnonewpeaks.Itispredictedthatthecrystallizationonlyoccursintheprojectedrangeofions.2.2AnalysisofprecipitationphaseFromindexingofdiffractionringsinFig.lbandFig.lc,theprecipitatephaseisanfcccrystallinestructure.InFig.ld,anadditionalbccphaseisfound(ring3,ring5andring8).Thecalculatedlatticeparametersforprecipitatephasesundervariousiondosesareasfollows:5×1016/cm2a=0.412nm(fcc)l×1017/cm2a=0.42lnm(fcc)5×1017/cm2a=0.428nm(fcc)l×1018/cm2a=0.478nm(fcc)a=0.292nm(bcc)UsingASTMindex,itisidentifiedthatthebccphaseisα-Fe(a=0.2866nm).Todeterminethefccprecipitatephase,weinspectedallcompoundswithfcccrystallinestructurecomposedofelementsFe,Ni,SiandB,foundthatthreecompoundsFeSi(a=0.446nm),FeNi3(a=0.353nm)andFe3Si(a=0.564nm),butthemostfavourablecompoundwasFeSi.Therefore,itisassumedthatthepreferentialprecipitatephaseisFeSi,andisfollowedbytheeutectcphaseα-Feundertheheliumionirradiation.2.3HeliumbubbledistributionThemorphologiesofheliumbubblesformedbyagglomerationofimplantedheliumionsareshowninFig.2.Thesmallblackdotspresentbubblesunderbrightfieldwiththeunderfocusingoperation.FromFig.2,itisrevealedthatbubbleslowerthedensity,butinflateinthedimensionwiththeincreaseiniondose.Moreover,underthehigherdosethebubblesjoinedtogether.Fig.3plotsthechangesofdensitiesanddiametersofbubbleswiththeiondose.ItisevidentthatthecriticaldosetoformbubblesinFe38Ni39Si10B13islowerthan5×1016/cm2,whichisslightdifferentfrom1×1017/cm2reportedbyTyagi[1].3.DiscussionAstheresultsreportedbyGusevaandGordeeva[4],theheliumirradiationcantrulybringonthepartialcrystallizationinmetallicglassFe38Ni39Si10B13belowitsordinarythermalcrystallizationtemperature.GusevaandGordeevaconfirmedthattheprecipitatesinFe40Ni40B20wasα-Fephaseunderheliumionirradiationof40keVenergyand5μA/cm2currentdensity,inwhichthetemperaturerisingofthesampleswaslowerthan200℃.Howerve,inpresentexperiment,thoughα-Fephaseisdetermined,notraceofM3B,M2BandMBprecipitatephaseisobserved,whichwasreportedbyaboveauthorsunderirradiationwithenergyof40keVandioncurrentdensityof30μA/cm2.Inaddition,theprecipitationprocessinpresentexperimentissomewhatdifferentfromtheprecipitationprocessreportedbyaboveauthors,thepreferentialprecipitationphaseisFeSi,andfollowedbytheeutecticphaseα-Fe.CrystallizationofamorphousFe40Ni40B20wasnotobservedbyTyagi,whichwasthesamematerialasthatusedbyGusevaandGordeeva,undertheirradiationwith100keVionenergyand30μA/cm2ioncurrentdensity[3].Itmayrelatetothetemperaturerisingofsamplesorsomethingelse.Accordingtothecomparisonandanalysis,itmaybeconcludedthatthecrystallizationofmetallicglassesisverysensitivetothetemperaturerisinginsamplescausedbyionbeamirradiation.ThereasonofthepreferentialphasetobeFeSiandfollowedα-Femaybethatinanamorphousmaterial,themetalloidelementsshouldkeepatthetotalcontentsabove20at%,otherwisesomeelementsorcompoundswillprecipitatetoremainthebalanceofchemicalcomposition.Therefore,astheprecipitationofFeSianddeclineofSicontentsinasample,FeandNimayprecipitateasaneutecticphaseaccordingtoaboveidea.Inthisexperiment,Feprecipitatedfirstly.ThedifferenceoflatticeparametersbetweenexperimentaldataandASTMstandarddatamayresultsintheexistencesofNiandBetcandincompletecrystallizationinsample.Thegeneralviewpointforirradiation-assisted-crystallizationofmetallicglassbelowtheirthermalcrystallizationtemperatureisthedisplacementdamagesinducedbycollosion-cascadebetweenincidentionsandtargetatoms.Thedisplacementdamagesprovidethenucleatingcentresandtheirradiation-assistedmigrationincreasesthecrystallizeddrivingforce,butnodirectrelationshipbetweenheliumandcrystallization.Thegrowthofagrainiscloselyattributedtothediffusionofneighbouringatomstothegrowingnucleus,whichisreliedonthetemperatureextremely,accordingly,thecrystallizationofmetallicglassisverysensitivetothetemperaturerisingfromionbeambombardmentinanirradiatedsample.4.Summary(l)TheFe38Ni39Si10B13metallicglasswillcrystallizebelowitsordinarythermalcrystallizationtemperatureunderheliumionirradiationwith100keVenergyand6μA/cm2ionbeamcurrentdensity.(2)ThepreferentialprecipitationphaseofthemetallicglassisFeSi,andfollowedbyaneutecticphaseα-Fe.(3)Thecriticaldoseformingheliumbubblesinthemetallicglassisabout5×1016/cm2,whichisslightlylowerthanthedosereportedbyTyagi.(4)Theirradiation-assisted-crystallizaofametallicglassesisverysensitivetothetemperaturerisingcausedbyionbeambombardmentinanirradiatedsample.Acknowledgements─TheauthorswouldliketothankthecolleaguesofIonImplantationGroupinChinaInstituteof.AtomicEnergy.forhelpinginsampleirradiation,alsotoProfe
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: Fe38Ni39Si10B13
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