粉末冶金钼管热挤压工艺基础研究

太原理工大学硕士学位论文粉末冶金钼管热挤压工艺基础研究姓名：张宏亮申请学位级别：硕士专业：@指导教师：许树勤20100401I(99.7%)()()Gleeble-3800110011501200125011.5s-117.3s-123s-18×12IIArrheniusZener-Hollomon70%(750850950)70%85060minDEFORM1250225mm/s8%D10%D11%D12%D55°60°65°70°10%D65°IIITheFundamentalResearchofHotExtrusionProcessforPowderMetallurgyMolybdenumTubeABSTRACTReducingreflectinglayer,transparentelectrode,emitterandcathodeintheLCDmanufacturingtechnologyareallcarriedoutusingsputteringmethod.Sputteringtargetisusuallymadeofpuremolybdenumsheet.Inrecentyears,withthegrowingsizeofLCDscreen,thevolumeofsputteringshapemolybdenumtargetincreasescorrespondingly.Ifmolybdenumtubeisusedastarget,thelengthofscreenisdependedonthelengthofmolybdenumtubewhilethewidthisunlimited.Toimprovetheuniformityofsputteredcoating,thedensityofsputteringtargetmustbeover99.7%.However,thecommonmolybdenumproducttechnologycannotmeetthedensitydemandfortargets.Therefore,hotworkingprocessisaddedtoraisethedensityofmolybdenumproducts.Inthispaper,thehotextrusionprocessisadoptedinthiswork.Inviewoflowdensityofmolybdenumproductspreparedbyhotextrusionprocessofpowdermetallurgicalmolybdenumtube,methodsofhigh-temperatureuniaxialcompressiontestcombinedwithfiniteelementIVnumericalsimulationareusedtoinvestigatethehotextrusionprocessofpowdermetallurgicalmolybdenumtube.Theresearchincludehigh-temperatureplasticdeformationbehaviorofpowdermetallurgicalmolybdenumbarsaswellasoptimizationofmolybdenumtubehotextrusionprocessandextrusiondiestructure.UniaxialcompressiontestwascarriedoutonGleeble-3800thermalsimulatorat1100,1150,1200and1250andatstrainratesof11.5,17.3and23s-1.Thesizeofpowdermetallurgicalmolybdenumspecimenis8×12.Thehigh-temperaturesteadyflowstressconstitutiveequationforpowdermetallurgicalmolybdenumbarswassetupbasedontheexperimentaldataandtheflowstressmechanicalbehaviorcharacteristicindeformationprocessisstudied.Resultsshowthat:powdermetallurgicalmolybdenumshowsobviouscharacteristicsofdynamicrecoveryandrecrystallizationinthehightemperaturedeformation.Molybdenumisstrainratesensitivematerial,thatis,flowstressincreaseswithincreasingstrainrate.Thehigh-temperatureplasticdeformationprocessofpowdermetallurgicalmolybdenumisthermallyactivatedprocesscontrolledbydislocationmovementsandcanbedescribedbyusingZener-HollomonparametersincludingArrhenius.Thedensityvariationsofdeformedpowdermetallurgicalmolybdenumbarsweretestedbyusingsuspendingweightmethod.ExperimentresultsshowthatpowdermetallurgicalmolybdenumbarscanmeetthedensitydemandoftargetVwhenthedeformationofpowdermetallurgicalmolybdenumbarsisover70%.Effectofheat-treatmenttemperatures(750850950)afterthermaldeformationonthemicrostructurewasinvestigatedbymicrostructureobservation.Microstructureanalysisshowsthat:Theoptimalprocessisannealingat850for60minwhentherelativedeformationofpowdermetallurgicalingotsis70%.Atthistime,mostgrainsoverlappedaccompaniedbyformationoffineequiaxedsubgrains.Mostbandedstructuresareretainedandresidualstressiseliminated,sotheperformanceisthebest.SimulationanalysisbyfiniteelementsoftwareDEFORMwasdonetooptimizetheextrusiondiestructureformanufacturingpowdermetallurgicalmolybdenumtubes.Theextrusionmoldwithdieanglesof55°,60°,65°,70°,straightdielengthof8%D10%D11%Dand12%D,extrusionspeedof225mm/sandextrusiontemperatureof1250weresimulated.Resultsshowthat:takingextrusionrate,tuberollingyield,all-incostsavingratioandstressandstrainstatusasstandard,theoptimaldiestructureisobtainedwhenstraightdielengthofflattapermoldis11%Danddieangleis60°.KEYWORDSmolybdenumconstitutiveequationhotextrusionfiniteelementsimulation1(2622)0.0120[1,2]1.1.1.1.1.1)[1]B95.94424d55s′1-12)[1]-1-23)[1]234566(1)475MO3(2)475700MO3XMO2(3)700800MO2(MO3)“”(4)850MO321-31-1Table1-1Physicalpropertiesofmolybdenumbcc3.14683.14768136g/cm310.2226224804·5.7×10-6112735.2×10-6212765.5×10-6/·0.3410000.320000.244.216002.5×10-825001×10-2/·200.05814000.0751/0205.3×10-625700(5.86.2)×10-61-2Table1-2Mechanicalpropertiesofmolybdenum0.324MPa322000MPa121800--404090%MPa6001100(1mm)MPa7202480(1mm)MPa600900()MPa25003200(1mm)MPa22502500(1mm)MPa18002000()31-3Table1-3ChemicalpropertiesofmolybdenumHF440HFH2SO4790H2HFCO1400CO21200HFHNO31100AlFeCoNiSnZnBi1100N2110011008402301.1.2.1778191020[3,4][5]480[6,7][8][9,10][11][12,13]1.1.3.1)[14](2620)(VAC)(EB)5(1)(2)(3)(4)(5)2)[15][16][17]()-(DBTT)[18,19]ddd-CNOOMO2NCC[20]()6(-)1.1.4.()()[20](1)(2)(3)(4)0.51.1.5.71-1Oa-ab-bc-Fig1-1Extrusionpressure-strokecurveduringextrusion(1-1)(1-1oa)ab1-1ab1-1bc[21]1)[21]()8342)[21](1)1-2ddNtdNzhdNgtτzhτgτdτrrrlrlgztdNdNzddfPlrrrrlrrdNt1-2Fig1-2Forces,stressanddeformationactingonthemetallσrσθσlσrσθσrεθεε91-2|lσ||lσ||lσ|rσlσ(1rlzhKσσ−=)1rzhKσ=1zhKKgθσrσrσ=θσlσrσ|lσ||rσ||lσ||rσ|(2)1-31-3Fig1-3Coordinategridchangesinextrusion10(1-3)1-31-4abcd7T11dbca2231122355667'7441-4Fig1-4Stagnantzoneintheextrusioncylinder7(1-4)776(1-4)77′3)[21](1)(1-4)7′127′dNttd1-51dNtt2abdNtdNtaatttt211b1-5Fig1-5Force’ssituationwhencentertailsbeformed(2)1-6(3)1-713121.2.——99.7%1910194540(R.Parke)(J.L.Ham)40605095%1-712Fig1-7Formationofsubcutaneoustails1-6Fig1-6Formationofrin