高熵合金PPT课件

.,1,FeCoNiCrMn高熵合金的组织稳定性及变形行为,吕昭平教授,北京科技大学新金属材料国家重点实验室,.,2,Acknowledgements,Students:W.H.Liu,S.Y.Li,H.L.HuangandZ.F.LeiCollaborators:H.Wang,Y.Wu,andX.J.LiuNationalsciencefoundationofChina(Nos.51010001,51001009,and51271212)“111”Program(B07003)ProgramforInnovativeResearchTeaminUniversity,.,3,Traditionalalloysaremostlybasedononeprimaryelement,Steels(Fe),Alalloys,Tialloys,Mgalloys,Supperalloys(Ni),.,4,Discoveryofhighentropyalloys,CantorBetal.MSEA,2004,375-377:213-218.,In2004,MulticomponentFeCoNiCrMnalloyfirstlyreportedbyCantorB.withasimplefccsolid-solutionstructure.,.,5,YehJWetal.AdvEngMater,2004,6:299-303.,Definitionofhighentropyalloys,Stillin2004,theconceptofhighentropyalloywasfirstlyintroducedbyYehJW,.,6,Simplephaseformationbutcomplexmetallurgicalphenomenon,Cu-Zrbinaryalloysystem,ActuallyHEAsalloyhaveasimplesolid-solutionstructure(mainlyfccorbcc)!,TheGibbsPhaseRuleP=N+1-FWhenN=5,P=6,FeCoNiCrMn,.,7,FeaturesofHEAsseverelatticedistortion,Zhou,etal.ApplPhysLett,2008,92:241917SenkovON,etal.Intermetallics,2011,19:698,.,8,Tsaietal.ActaMater2013;61:4887,ConstituentelementsintheHEAmatrixdiffusemuchslowlyovertheentiretemperaturerangeThediffusioncoefficientofNiisthesmallestamongthatofallconstituents,FeaturesofHEAssluggishdiffusion,9,Senkovetal.Intermetallics2011;19:698-706,As-cast,Aftercompressionat1073K,FormationofasinglebccphaseThebccphaseishighlystableupto1600oC,1400oC19h,FeaturesofHEAshighphasestability,10,FeaturesofHEAscocktaileffect,theeffectindicatesthattheunexpectedpropertiescanbeobtainedaftermixingmanyelements,whichcouldnotbeobtainedfromanyoneindependentelement.,11,ExtremelyhightoughnessofatypicalfccHEA,BerndGludovatzetal.Science2014,345:1153,ThefracturetoughnessofFeCoNiCrMnexceeds210MPam-1/2,12,Abnormallow-temperaturemechanicalproperties,Withthedecreaseoftestingtemperature,bothtensilestrengthandductilityareincreased;Thefracturetoughnesskeptalmostunchanged;,13,Highyieldstrengthattemperaturesupto1600oCThestrongresistancetohigh-temperaturesoftening,ascomparedtothesuperalloys,Promisinghigh-temperaturemechanicalpropertiesofbccHEAs,Senkovetal.Intermetallics2011;19:698-706,14,Ta34Nb33Hf8Zr14Ti11HEApossessesanbody-centeredcubicstructureoflatticeparametera3.36.ItisatypeIIsuperconductorwithatransitiontemperatureTc7.3K,P.Koeljetal.PRL2014,113:107001,InterestingphysicalpropertiesofHEAs:discoveryofsuperconductivity,15,Diffusionbarriermaterials,Highphasestability-nointeractionwithsubstrates;Lowdiffusionkinetics-highdiffusionresistanceatelevatedtemperatures,16,TheresearchactivitiesonHEAsatUSTB,ProgressinMaterialsScience,2014;61:1-93,17,OurpurposeDesigntheFeCoNiCrMnbasedHEAsforhigh-temperatureapplications,ContentPhaseformationandstabilityGraingrowthatelevatedtemperaturesDeformationbehaviorAlloyingeffects(toenhancehigh-Tmechanicalperformance),PhaseformationandstabilityareinfluencedbynotonlychemistrybutalsoprocessingconditionsEffectsofalloyingadditionsonphaseformation,stabilityandpropertiesarenotassimpleasexpected,18,Phaseformationintheas-castFeCoNiCrMn,Basicallythealloyhasasinglefccphasebutwithasmallfractionofunidentifiedphase(Cr2Mnoxide?),19,TheFeCoNiCrMnhighentropyalloyshowedhighphasestability,ThesinglefccphaseintheFeCoNiCrMnalloyisstableevenafter30daysannealingat950oC,20,TheFeCoNiCrMnhighentropyalloyshowedhighphasestability,TextureseemschangedwiththeprocessingconditionsNosecondphasewasformedduringtherolling/annealingprocesses,21,ContentPhaseformationandstabilityGraingrowthatelevatedtemperaturesDeformationbehaviorAlloyingeffects,22,850C/1h,850C/2h,850C/2h,70%coldrolled,925C/1h,925C/2h,925C/3.5h,GraingrowthbehavioroftheFeCoNiCrMnhighentropyalloywasstudiedindetail,23,GraincoarseningexhibitedaclassicalpowerlawbehaviorintheFeCoNiCrMnalloy,n=3andD0=1.0mmnislargerthan2whichisforthe“ideal”graingrowthinsingle-phasepurematerials,Liuetal.,ScriptaMaterialia2013;68:526,24,Theapparentactivationenergyforgraingrowthsuggeststhatsluggishdiffusionindeedoccurred,TheQvalueismuchhigherthanthatforAISI304LNstainlesssteels,whichisonlyabout150kJmol-1,25,ThehardnessvaluesatdifferenttemperaturescloselyfollowtheclassicalHallPetchrelationship,ThesofteningmainlyfromgraincoarseningTheKHPislargerthan600Mpamm-0.5(theupper-boundforfccmetals),suggestingthatgrainboundaryhardeningefficiencyisobviouslyhigher,26,ContentPhaseformationandstabilityGraingrowthatelevatedtemperaturesDeformationbehaviorAlloyingeffects,27,In-situneutrondiffractionstudyofdeformationbehavioroftheFeCoNiCrMnalloywasconducted,Wuetal.,Appl.Phys.Letts.2014;104:051910,VULCANsystematSpallationNeutronScattering,OakRidgeNationalLaboratory,28,Modulus:GPa,Strongelasticanisotropywasobservedduringthetensileloading,ThelatticestrainchangeisstronglydependentonthegrainorientationsThe200planeshavethelowestelasticmoduluswhilethe331planeshavethehighestYoungsmodulusanisotropy(E111/E100)is1.98,closetothatofNi(2.17)butsmallerthanthatoftypicalfccsteels(3.20),29,Developmentofatexturedstructureduringthetensiledeformation,Thepeakintensityofthe220and200reflectionsdecreased,whilethatofthe111reflectionsincreasedTexturalevolutionofthecurrentHEAduringtensionappearstobesimilartothoseoftypicalFCCmetalsandalloys,forexample,polycrystallinecopperwithcolumnargrains,30,ThesinglecrystalelasticconstantsofthecurrentHEAweredeterminedbytheKronersmodel,Thecubicelasticanisotropyfactor,Theshearanisotropywascalculatedas2.84,muchsmallerthanthatoftheternaryFeCrNialloy(3.77),butclosetothatofthepureFCC-Ni(2.51),manifestingthattheelasticanisotropybehaviorofthecurrentHEAisclosetothatofitsFCCcomponent,i.e.,pureNi.,31,Theexperimentallydeterminedpeakbroadeningdatacanrevealthedislocationtypesduringdeformation,Theslopeintheaboveplotis2.189,whichseemslikeabalancingvaluefortheedge(1.492)andscrew(2.298)dislocations,butclosetothatofthescrewdislocationArepresentativebrightfieldimagewithwiggleddislocationsinadeformedspecimen,suggestingamixeddislocationcharacteristics,32,Flowbehavioratdifferenttemperaturesandstrainrateswereinvestigated,Thetemperatureisinbetween1023and1123KThestrainraterangesfrom6.41010-7to8.01310-4s-1,Heetal.,Intermetallics55,2014;9-14.,33,TheNortonEquation,Steady-statedeformationbehaviorofFeCoNiCrMn,RegionIIwithahighstressexponentatthehighstrainrates(orstresses)whileRegionIwithalowstressexponentatthelowstrainrates(orstresses)Theactivationenergyintworegionsarecomparabletothatforlatticediffusion.Forexample,Ni(317.5kJ/mol),Cr(292.9kJ/mol),andMn(288.4kJ/mol),34,Thenormalizedplotindicatesthatthedataobtainedatvarioustemperatures(1023-1123K)collapseintoonesinglemastercurve,Inthehighstrainrateregime,nis5andtheactivationenergyis330kJ/mol,suggestingadislocation-climbmechanismandtheslowestdiffusingspeciesNicontrolstherateprocess.Inthelowstrainrateregime,nis3andtheactivationenergyis280kJ/mol,suggestingthatthemechanismisthedislocationglidingandthedeformationrateiscontrolledbythediffusionofoneoftheconstituentelementswhichactsasthesoluteatom.,35,ContentPhaseformationandstabilityGraingrowthatelevatedtemperaturesDeformationbehaviorAlloyingeffectsAleffects,RelativelylowersteadystateflowstressthansuperalloysOxidationresistanceislowduetohighlyactiveelementMn,36,AdditionofAlinthe(FeCoNiCrMn)100-xAlxalloysinducedaphasetransitionfromfcctobccstartingatAl8,Heetal.,ActaMater.2014;62:105.,37,MicrostructureobservationfurtherconfirmsthephasetransitionresultedfromtheAladdition,BccphasebecomesdominantinalloyAl13,Al14andAl16,andtheminorfccphasemainlyliesinthebccgrainboundaries.,38,Thecubic-shapedparticlesareorderedB2whiletheinter-precipitateareaisdisorderedA2.fcc:74.6%.,TEMcharacterizationrevealsthedetailedphasecharacteristics,Thecubic-shapedprecipitatesbecomeslightlysmallerbutmoreclose-packed.fcc:11%AlaretoobrittletobedeformedduetoformationoforderedBCCstructures.,43,Summary,FeCoNiCrMnalloy,Phaseformationandstability-high(homogenization,longtermaging,rolling),Graingrowthathightemperatures-slow,Aleffects-solutionstrengthening,Deformationbehavior-RT:similartoNi,mixdislocationsHT:highstrainrate,dislocationclimblowstrainrate,dislocationglide,High-Tmaterials,44,Secondaryphasehardeningresultedfrombccphases(NiAlB2)inFeCoNiCrMnisnotverysatisfactory.Basedonpreviousstudiesinsteelsandsuperalloys,L12phase(phase-Ni3Al)isadesirabl