DOC

stainless steel functionally graded materials

By Dale Young,2014-02-18 23:10
6 views 0
stainless steel functionally graded materialssteel,Steel

    stainless steel functionally graded materials J.Cent.SouthUniv.Technoi.(2009)16:08920896

    DoI:10.1007/sll771O0901486Springer

    Flexuralstrengthofzirconia/stainlesssteelfunctionallygradedmaterials LIJun(李军),ZHAOKang(赵康),TANGYu.feiQ~j5E,),LIDayu(李大玉)

    (SchoolofMaterialsandEngineering,Xi'anUniversityofTechnology,Xi'an710048,China) Abstract:Zirconia/stainlesssteel(Zr0JSUS3l6L)functionallygradedmaterials(FGMs)werefabricatedbytapecastingand

    laminating.MicrostructuresofFGMswereobservedbyopticalmicroscope.FracturebehaviorofFGMsindifferentloadingmodes

    andinfluencesofdifferentgradientchangesonflexuralstrengthwereinvestigated.TheresultsshowthatZrO,/SUS316LFGMswith

    gradedcomponentsatinterlayersareobtainedaftertheyaresinteredinvacuumandpressurelessconditionat1350?.TheIII

    mixedmOdecrackcreatesincompositelayerandgrowstobothsideszigzagwhileloadingonZr(),layer.Flexuralstrengthsare

    496.4,421.7and387.5MPawhengradientchangesare10%,15%and20%,butflexuralstrengthsofthecorrespondingfracture

    layersare387.1,334.6and282.3MPasincecracksofFGMsareaffectedbythree.dimensionalstress.respectively.Thecracksare

    generatedinZrO2layerandextendtoSUS316LlayerwhileloadingisaddedonSUS316Llayer.flexuralstrengthdoesnotchange

    withthegradedcomponentsandkeepsconsistentbasically.

    Keywords:Zr02;functionallygradedmaterials;flexuralstrength;fracture;tapecasting 1Introduction

    Defensivequalityofarmorsisfacingasevere

    challengewiththedevelopmentofcounter.arlnor

    weapontechnology[1]./~A'lllormaterialsrequirenotonly excellentantipenetrationpropertybutalsolowerdensity andhighspecificstrength[23.Ceramic/metal

    compositeshaverecentlybecomearesearchfocussince meycansatisfytherequirementofperformances. Ceramic/metalarmorcomposites[4-61areadhesive compositesfabricatedwithceramicplateandmetalplate. Stressconcentration,asaresultofpoorwettability betweenmetalandceramicininterlayers,however, resultsindelaminationfractureandspalling,andreduces theperformancesofarmormaterials.Ceramic/metal functionallygradedmaterials(FGMs)[7llwithgraded

    componentsinthethicknessdirectioncannotmake failureofphysicalproperties,whichcanavoid interlaminarstressorscalestressconcentratedown.It wasreportedthattheceramic/metalFGMsdisplayed higherresistancetocrackgrowth,andhadgood anti-penetrationpropertyasarmormaterials[12]. StrengthandfracturemechanismofFGMsaresome ofnewsubjectsinvolvingmaterialmechanics[1314].

    ZHANGetal[15-161investigatedfracturesonmodeI crackandmodeIIcrackrespectivelyinFGMsby

    theoreticalanalysis.NIKHILetal[171reportedflexural propertiesoffunctionallygradedsyntacticfoams. Interestingresultswereobtainedfromthereferred studiesandtheflexuralstrengthwastestifiedtobeafine approachtoevaluatemechanicalpropertiesofFGMs. However.fracturebehaviorsandflexuralstrengthof metal/ceramicFGMsindifferentloadingmodesare seldomreported.

    Inthiswork.thezirconia/stainlesssteel(ZrO2/ SUS316L)FGMswerepreparedbytapecastingand laminating.Microstructureswereobserved.Fractureof FGMsindifferentloadingmodesandinfluencesof variousgradientchangesonflexuralstrengthwerealso investigated.

    2Experimental

    2.1SoecimenpreparationofFGMs

    3%Y,O3-dopedpartiallystabilizedzirconia(PSZ.in molefraction)powderfromNaboCorp.,China,was usedasceramicrawmateria1.andstainlesssteel316L powder(sus316L),fromAisierCorp.,China,wasused asmetalstartingmateria1.ACLB01organicbinderas

    anadditivewasusedfortapecasting[181.Specimensof FGMswerepreparedviathechangedcomponent distributedfromZr0,t0SUS316L,asshowninFig.1. Theamountsoforganicadditivesforslurrieswere calculatedfromthoseofZrO2andSUS316Lslurriesin proportiontoZrO,volumefraction.Thedispersedslurry wascastontoabaseplateanddriedslowlyinahumid roomtoavoidgeneratingcracksinthegreensheet. Greensheetswerestackedintoadieandthenpressedat 20MPaand70?,resultinginaFGMsbakedbOdyafter burned.outprocessinfumace(modelGSL1600X.China) at600?.ThebakedFGMsbodywassinteredin

    Foundationitem:Project(2007K06

    13)suppoaedbytheScienceandTechniqueResearchandDevelopmentProgramofShaanxiP

    rovince,China

    Receiveddate:20090122;Accepteddate:2009-0619

Correspondingauthor:ZHAOKang,Professor,PhD;Tel:+8629

    82312601;Email:kzhao.xaut@gmail.com

    J.Cent.SouthUniv.Techno1.(2009)16:08920896893

    vacuumatabout1350?for3h

    Fig.1VariouscomponentschangedofZrO2:(a)l0%;(b)15% (c)20%

    2.2Characterizati0n

    Themicrostructuresandcrackpropagationpathsof thepreparedFGMswereexaminedwithanoptical microscope(GX71,0LYMPUS,Japan).Theflexural strengthwasstudiedusingthreepointbendingtestby

    computerservocontrolmaterialtestingmachine (HT2402100KN,Taiwan,China).Thethicknessof FGMswas3mm,thespanwas20ITUTIandthepunch ratewas0.2mm/min.Theflexurals~engthwastestedby twofashionswhileloadingonZrO,layerandSUS316L layer,respectively.Loadingmodesofflexuralstrength testareshowninFig.2.

    Theflexuralstrengthiscalculatedbythefollowing formula:

    3

    f=r1,

    2bh

    whereo'fistheflexuralstrength;Pisthemaximum load;Listhespanlength;andhandbarethicknessand widthofFGMs,respectively.

    ZrO2

    SLjS316L

    SUS316L

    ZrO2

(a)

    (b)

    Fig?2Loadingmodesofflexuralstrengthtest:(a)Loading modeA;(b)LoadingmodeB

    3Resultsanddiseuss~en

    3.1MicrOstructure

    MicrostructuresofZrO2/SUS316LFGMswith

    variousgradientchangesareshowninFig.

    3.InFig-3(a),

    gradientchangeofFGMsis10%(volumefraction),and whiteregionrepresentsSUS316Landtheblackregion representsZrO2.Thecompositiongraduallychanges fromSUS3l6LlayertoZrO,layer.Theinterfacesare eliminatedbvdisingcomponentsfromhigh

    concentrationtolowconcentrationalthoughthe componentofZrO,orSUS3l6Lwiththechange

    contrastofvolumefractionofl0%existsinadjacent 1ayers.andthemicrostructurebetweenlayerschanges continually.Theflawsarenotobservedininterlayerof FGMswithbe~erbonding.Therearesomeporesinthe FGMssinteredundervacuumandpressurelesscondition. Theporescanberemovedbypressuresintering[19]. OthergradientchangesofFGMsdisplaythesimilar regularity,asshowninFigs.3(b)and(c).Discontinuity ofphysicalpropertiesatinterfacecanbeeliminateddue tothediffusionofthecomponent.

    Fig.3Microstructuresofzirconia/SUS316LFGMswithvarious gradientchanges(ZrO2):(a)1O%;(b)15%;(c)20% 3.2FracturesofFGMsindifierentloadingmodes CrackpathsofZrO,/SUS316LFGMswith20%

    gradientchangeforthree-pointbendingexperimentare showninFig.4.Thecrackinitiationandpropagationpath arevarioussincegradedlayersofFGMswithdifferent performancesareactedoncrackpropagation.InFig. 4(a),

    thecrackiscreatedin20%Zr0,/80%SUS316L

    compositelayerandgrowstobothsidesinloadingmode

    894J.Cent.SouthUniv.Techno1.f2009116:08920896

    crackextendsthroughlayersandisdeflectedin interlayerfromcrackinitiationtoZr0,andSUS316L. respectively.

    ThethicknesshofFGMsshouldbemodified.The formulaofpracticalflexuralstrengthisasfollows: A.ThecrackisIIImixedmodecrackduetonormal

    stressandshearstresseffect.Thecrackpathispolygona1 lineandthesectionofFGMsisstaggering.Itisfurther foundfromtheobservationofcrackextensionpathsthat crackdefectionsimprovethefracturework.The destructibilityofcrackdecreasesandfailureofFGMsis avoided.Theresultshowsabetterresistancetocrack jnitiation.

    Fig.4CrackpathsofZrO2/SUS3l6LFGMsforthreepoint

    bendingexperiment:(a)LoadingmodeA;(b)LoadingmodeB InFig.4(b),thecrackisgeneratedin100%Zr02 laverandgrowstoSUS316Llayer.Thecrackis

    propagatedrapidly,butsomedeflectionsareformedwith theincreaseofSUS316Lcontent.Thissuggeststhatthe SUS316Lcanpreventthecrackfrompropagating.The delaminationfracturephenomenonininterlayerandthe crackthroughoutFGMsalonggradientdirectionlike

    homogeneousmaterialscannotbeobserved.Moreover, flakingdamagedisgeneratedaroundcrackpathbecause oftheipintofinnerairholeandmicrocrackinitiatedby crackgrowth.

    DiagramsofcrackextensionofZr02/SUS316L FGMsindifferentloadingmodesareshowninFig.5.In Fig.5(a),thecrackiscreatedininterlayerinloading modeA.Generally,thecrackshouldbecreatedin SUS316Llayerlocatedatthemaximumtensilestress. However.elasticdefc)rmationoccursinSUS3l6Llayer becauseofitsgoodductility.Zr()2/SUS3l6Lcomposite 1ayerisfracturedbe:foreSUS3l6Llayersincethe ductilityofthecompositelayerislessthanthatof SUS316L1ayerwhilebearstensilestress.Andthen, ,

    3PL

    

    2bh'2(2)

    where;isthepracticalflexuralstrengthofFGMsin loadingmodeA:histhedistancefromcrackinitiation toloadingpointmeasuredbymicroscopicobservation. InFig.5(b),onthecontrary,thecrackisgenerated inZrO2layerandextendstoSUS316Llayerinloading modeB.ThebrittleruptureoccursinZrO,layerlocated atthemaximumtensilestresssinceZrO,isatypical brittlemateda1.Thefractureresistanceincreaseswiththe crackextendingtoSUS316Llayerthatundergoesplastic deformationfinallv.

    ZrO2

    SUS316L

SUS3l6

    Zr0

    (a)

    (b)

    Fig.5DiagramsofcrackextensionofZrO2/SUS316LFGMs (a)LoadingmodeA;(b)LoadingmodeB

    3.3FlexuralstrenttthofFGMs

    Fig.6showstherelativedisplacementwith1oading whenthreepointbendingtestofspecimenwith20% gradedchangeiscarriedout.InFig.6(a),relative displacementincreaseswiththeincreaseofloading.In SUS316Llayerelasticdeformationfirstlytakesplace duetoitsplasticproperty,andthenplasticdeformation occurswhenrelativedisplacementarrivesat0.235llnTl, butnocrackinitiates.Thecrackisgeneratedin 20%Zr02/80%SUS3l6Lcompositelayerwhenrelative displacementarrivesat0_291mm.andintheSUS316L layerplasticdeformationoccurs.Thecrackextendswith theincreaseofloading.ThefailureofFGMsisaccrued whenrelativedisplacementardvesat0.707illn1. InFig.6(b),relativedisplacementincreasesrapidly withtheincreaseofloading.AbruptfailureofFGMsis producedwhenrelativedisplacementis0.0471TnTI. BecauseZr(),isatyoicalbrittlematerialthecrackis generatedinZrO,layerandthebrittlefractureOCCurS. J.Cent.SouthUniv.Techno1.(2009)16:08920896895

    Theregularityoffracturebehaviorswithothergraded changesissimilartothatwithgradedchangeof20%. ?

.

    0

    -d

    g

    J

    Displacement/mm

    Displacement/ram

    Fig.6TrialcurvesofthreepointbendingtestofZrO2/SUS316L FGMswith20%gradedchange:(a)LoadingmodeA;(b) LoadingmodeB

    TheflexuralstrengthofFGMsinloadingmodeBis calculatedaccordingtoEq.(11.Andflexuralstrengthof FGMsinloadingmodeAisobtainedbyEq.f21.As showninTable1.theflexuralstrengthdecreaseswith theincreaseofgradientcomponentinloadingmodeA. Themaximumoftheflexuralstrengthis496.4MPaat gradientcomponentofl0%andtheminimumis

    387.5MPaatgradientcomponentOf20%.Thisis becausewhenSUS3l6Lcontentofpositionwherecrack isgeneratedishighertheflexuralstrengthwillincrease withtheincreaseofthecontentofSUS316Landthe minordifferenceinadjacentlayersofFGMs.However. theflexuralstrengthbasicallykeepsaconstantbecause alltheinitiationsofcracksarelocatedatZrO,layerwith variousgradientchanges.Ingeneral,theflexuralstrength in1oadingmodeBislessthanthatinloadingmodeA sincestrengthofZrO2/SUS316Lcompositesislarger thanthatofZr0,.

    Thepositionofcrackinitiationiscalibratedby microscopicobservationatvariousgradientchangesin

    loadingmodeA.TheflexuralstrengthofZrO2/SUS316L compositelayercorrespondingtothepositionof producingcracksiscalculatedaccordingtoEq.(1),and finallytheflexuralstrengthofFGMsiscompared.As showninTable2.theflexuralstrengthofFGMsislarger thanthatofZr02/SUS316Lcompositelayerwith componentcorrespondingtothepositionofcrack initiation.Theflexuralstrengthofthecorresponding fracturelayeraccountsfor73%-79%ofthatofFGMs. Thecrackpropagationisaffectedbythree.dimensional stresses:thetensilestressproducedbybendingtest;the shearstressduetodifferentcomponentsofgradient layers;andthecompressionstressofSUS316Llayer. ComparedwiththatofZr0,/SUS316Lcompositelayer. theflexuralstrengthofFGMsisincreased.Moreover. Zr02/SUS3l6LFGMshavegoodmechanica1properties sincetheyhavebetterwettabilitybetweenZrO,and SUS316L[20].

    Table2FlexuralstrengthofFGMswhenloadingonZrO2layer (;)andcorrespondingfracturelayer(

    4Conclusions

    r1)Cracksarecreatedincompositelayerswith volumefractionofZrO,being10%.15%and20%

    respectivelyinloadingmodeAandextendtotwosides intheformofIIImixedmodecrack.

    f2)Flexura1strengthsofFGMsinloadingmodeA determinedbypostcorrectivethicknessare387.1.334.6 and282.3MPawithvariousgradientchangesof10%. 15%and20%.respectively.Flexuralstrengthsofthe correspondingfracturelayerarelessthanthoseofFGMs

Report this document

For any questions or suggestions please email
cust-service@docsford.com