research plan(english version)

1联合培养博士研究生研修计划ResearchPlanforPhDJointTrainingProgram姓名/Name姓/Surname：名/Firstname:性别/Sex出生日期/Dateofbirth(yy/mm/dd)所在院系/School/Department所学专业/Major国内导师/Domesticsupervisor留学国别/Hostingcountry留学国外大学/Hostinguniversity留学院系/Hostingfacultyordepartment国外导师/Hostingsupervisor研究领域/Researcharea学习期限/Durationofstudy12months(from2009.09to2010.09)研究课题名称/Researchtitle：SurfaceplasticdeformationregularityandthemicrostructuralevolutionoftheTiAlbillet研究背景/Researchbackground：Inthelightofmicrostructure,directionalsolidificationmicrostructuresexhibitoptimumcreepresistance.ExperimentalresultsindicatethatthecreeprateofdirectionallysolidifiedTiAlis10to1000timeslowerthanthatoftheordinaryfoundryalloys.Finegrainedstructurescanimprovethefatiguelimit,becausethefinegrainscanretardtheformationoffatiguecracksandthelargernumberofgrainboundariesassociatedwithfinegrainscanimpedetheextensionofcracks.Incontrast,mono-microstructurescanimproveotherproperties,suchascreepresistance.Consequently,compoundmicrostructuresarenecessarytomeetthedualdemandsofhighcreepresistanceandfatiguelimits.Ifthecompoundmicrostructurescanbedeveloped,itisanticipatedthatthemechanicalpropertiesofTiAlbilletswillbegreatlyimproved.申请人科研准备工作概述/Scientificpreparationsoftheapplicant：InordertoobtaincompoundmicrostructuresinTiAlbillets,namelyfinerecrystallizedgrainsonthesurfaceandtheoriginaldirectionallysolidifiedmicrostructureinthecenter,itisnecessarytointroducelocalizedplasticdeformationonthesurface,whileavoidingplasticdeformationinthecenter.Followingthissurfacedeformation,colddeformedbilletsaresubjectedtovacuumheattreatmentattemperatures+10℃～+20℃abovetheαtransuslineinordertoobtainthefinegrainswiththefullylamellarstructures,forthiskindofmicrostructureshaveoptimumcreepresistanceandfatigueproperty.ThreedifferentsurfaceplasticdeformationtechniqueshavebeendevelopedatHITincluding:controlledshotpeening,ballmilling,andthesurfaceextrusionmilling.EquivalentstrainandtheMisesstressregularityweremeasuredexperimentallyandsimulatedusingFEM(withABAQUS-6.7).Theresultsindicatethattheplasticdeformationislocalizedwithinthedepthof0.5mmandthemaximumequivalentstrainsofthecontrolledshotpeening,ballmillingandthesurfaceextrusionmillingextendupto0.11,0.7,0.045，respectively.Andwealsodid2someexperimentswiththetransmissionelectronicmicroscopy(TEM)onthecolddeformedsamples,whichshowsthatthereareplentyofdislocationtanglesonthetreatedsurface.Theseresultsindicatethatthereismuchdistortionenergyonthetreatedsurface.Themetallographyofthecolddeformedandtheheattreatedballmilledandsurfaceextrusionmilledsurfacesshowsthatfinegrainsoccuronthesurfaceofthebillet.TheobjectiveofmyresearchistostudythemicrostructureevolutioninshotpeenedofTi-46Al-0.5W-0.5Sibillet.出国学习预期目标，科研方法及时间安排/Expectedgoal,researchmethodsandarrangements：1.TodateIhaveprocessedseveralbilletsatdifferentcolddeformationparametersandhaveobservedthemicrostructureusingopticalmicroscopy.Thesestudieshaveexaminedvariationsintheshotpeeningparameters.IhavealsosimulatedtheshotpeeningprocessesasafunctionoftheexperimentparameterswithABAQUS-6.7toobtaintheequivalentstrainandMisesstressregularity.AtMSUIplantoanalyzetheinfluenceofthedifferentcolddeformationparametersonthelamellarandequiaxedgrainstructureswithscanningelectronmicroscopy(SEM),therebydevelopinganunderstandingofthecorrelationbetweentheequivalentstrain,Misesstress,andthemicrostructuresafterthecolddeformation.(September2009toDecember2009)2.Shotpeeningisatechniquethatdevelopsverylarge,yetlocalzonesofloadingandplasticdeformation.Afterthecolddeformation,thedegreeofdeformationindifferentzonesisnotidentical.Thereistypicallyadeformedzone,anundeformedzone,andatransientzone,withsignificantvariationsinmicrostructurebetweenthesezones.AtMSUIwillusescanningelectronmicroscopy(SEM)andtheassociatedtechniquesofelectronbackscattereddiffraction(EBSD)andelectronchannelingcontrastimaging(ECCI)tostudythesemicrostructures.Inparticular,IwilluseEBSDtoassessthecrystalorientationsandlocalcrystallographictextures,whileusingECCItostudythenatureofthedeformationinthegrains.(January2010toMarch2010)3.Heattreatmentofheavilydeformedmaterialstypicallyresultsinthegrowthofnew,defectfreegrains,oftenwithcrystalorientationssignificantlydifferentthanthoseofthedeformedgrains.AtMSUIwillstudytheeffectofthevacuumheattreatmentattemperature+10℃～+20℃abovetheαtransuslineontherecrystallizationandmicrostructureevolution.SEMandEBSDwillbeusedtostudythemicrostructureandgrainorientationduringthisprocess.Usinganin-situheatingstageavailableatMSU,Iwillstudythismicrostructureevolutioninrealtimeonselectedsamples.(April2010toJune2010)4.InordertounderstandthecorrelationbetweenthemicrostructuresandthemechanicalpropertiesIcarryouttensileandhardnesstestsonboththecold-deformedandtheheattreatedbillets.(July2010toSeptember2010)拟留学院校在此学科领域的水平和优势/Levelandadvantageofthehostinginstitutiononthisproject：ItisofcriticalimportanceindevelopingcompoundmicrostructuresforsimultaneouscreepresistanceandhighfatiguestrengthsintheTiAlalloystounderstandthenatureofthemicrostructureasafunctionofsurfaceheattre