外文翻译--搅拌摩擦焊搅拌头在材料流动和焊缝形成时的作用 英文版.pdf

MaterialsScienceandEngineeringA485(2008)367374TheroleoffrictionstirweldingtoolonmaterialflowandweldK.Kumar,SatishInstituteformAbstracttoolinthereenfltogethergibasedis2007ElsevierB.V.Allrightsreserved.K1.cessaluminiumjoiningwithnoconsumables.Ingeneral,theprocessiscarriedoutbyplungingarotatingFSWtoolintotheinterfaceoftworigidlyclampedsheets,untiltheshouldertouchesthesurfaceofthematerialbeingwelded,andtraversedalongtheweldline.Thefrictionalunderfrictionaldeformationethesimilarisgeometrytoolandmallystirturalafparenteterswhichcontrolsthematerialflowandheatinput,andinturnthequalityoftheweld.Buffaetal.2numericallyinves-tigatedtheeffectoftoolpinangleonvariousweldzones,grainsizeandweldingforces,andtheyhadshownthatthereisagood0921-5093/$doi:heatanddeformationheatareutilizedforthebondingtheappliednormalforce1.Theprimaryheatsourceisheatfromtoolshoulderandsecondaryheatsourceisheatfromthetoolpin2.TheprocessandterminologyofFSWareschematicallyxplainedinFig.1.Theadvancingside(AS)isthesidewherevelocityvectorsoftoolrotationandtraversedirectionareandthesidewherethevelocityvectorsareoppositereferredasretreatingside.Theprocessparametersaretool,axialforce,toolrotationspeed,traversespeedandtiltangle.Tooltiltangleistheanglebetweenthetoolaxisthenormaltothesurfaceofthesheetsbeingwelded.Nor-Correspondingauthor.Tel.:+918022932301；fax:+918023600648.E-mailaddress:satvkmecheng.iisc.ernet.in(S.V.Kailas).agreementbetweentheresultsofexperimentandthemodel.TheexperimentalworkcarriedoutbyKumarandKailas7usingdifferenttoolgeometryexplainstheeffectofshoulderdiameter,pindiameterandpinprofilesonsizeandlocationofdefects,mechanicalpropertiesandfinalgrainsize.But,thereisnotenoughconceptualbackgroundavailableonFSWtooldesign.Inmostoftheresearcharticlesthetoolgeometryisnotreportedduetovariousreasons.AsMishraandMa8pointedout,mostofthetooldesignisbasedonintuitiveconcepts.ThefirststepinderivingtheconceptofFSWtooldesignistounderstandtheroleoftoolinfrictionstirweldformation.Insolid-statewelding,theacceptedprincipleofweldfor-mationisstatedthatthebondingoccurs,whenapairofcontamination-freesurfacesarebroughttogetherintherangeofinter-atomic-distancesandtheforceutilizedforbondingistheinter-atomicforce9.Inmostofthesolid-stateweldingseefrontmatter2007ElsevierB.V.Allrightsreserved.10.1016/j.msea.2007.08.013DepartmentofMechanicalEngineering,IndianReceived30January2007；receivedinrevisedInthisinvestigationanattempthasbeenmadetounderstandthemechanisminit.Thishasbeendonebyunderstandingthematerialflowpatternfrictionstirweldingtoolwiththebasematerialiscontinuouslyincreased.gimesinvolvedinthefrictionstirweldformation；namely“pin-drivtoformadefect-freeweld.Theetchingcontrastintheseregimesonthematerialflowcharacteristicsamechanismofweldformationeywords:Frictionstirwelding；Materialflow；Mechanism；Defects；TooldesignIntroductionTheenvironmentfriendlyfrictionstirwelding(FSW)pro-isapotentialandprovenmethodforweldinghigh-strengthalloys.Thissolid-statelocalizedthermo-mechanicalprocessispredominantlyusedforbuttandlapjointsformationV.KailasofScience,Bangalore560012,India30July2007；accepted8August2007offrictionstirweldformationandtheroleoffrictionstirweldingtheweldproducedinaspecialexperiment,wheretheinteractionofTheresultsshowthattherearetwodifferentmodesofmaterialflowow”and“shoulder-drivenflow”.Thesematerialflowregimesmergevesrisetoonionringpatterninfrictionstirwelds.Inadditiontothatproposed.,themicrostructuralinvestigationrevealsthatthefrictionweldmenthasfourdifferentregionsbasedonthemicrostruc-features,namelyweldnugget(WN),thermo-mechanicallyfectedzone(TMAZ),heat-affectedzone(HAZ)andbaseormaterial36.Toolgeometryisconsideredtobeoneoftheprimeparam-368K.Kumar,S.V.Kailas/MaterialsScienceandEngineeringA485(2008)367374process,ing,thecontactinterfprocessisfyadditionalbodyarecoalescedture,theonlyysisthecomputationaltheFSWflomarkals.suitableorinitialmaterialtheand19offlocontribal.microstructuraltion20ringformationcofcylindersresultsintheonionringpattern.Fratinietal.20explainedthereasonfortheonionringpatternusingnumer-icalmodelthatthematerialenteringfromtheretreatingsideenterstheactionvolumeandrotatesatthebackofthetool.But,ingeneral,thereisnoexperimentalevidencethatcon-firmsthemechanismofonionringformationproposedbytheresearchers.stir23grooformationandformationinsufinformationformation.posedstirresearch,markmechanismsand2.alloAlZnMgturalalloThewithfrustumdiameterpinetryHDSweldingareThemachinebaseincreasingmaterialangleFig.1.Schematicoffriction-stirweldingprocessandterminology.likeforgewelding,diffusionwelding,frictionweld-explosivewelding,ultrasonicwelding,rollbonding,etc.,bondingisestablishedbygeneratingfreshmetal-to-metalbyeliminatingoxidelayersandimpuritiesfromtheaceunderrequiredpressureandtemperature10.Theseconditionsmodifythebasematerialinterfacetosat-thesolid-stateweldingcondition,anddonotgenerateanysurfacesinthematerial.Incontrast,duetothethird(theFSWtool)interactioninFSW,additionalinterfacesgeneratedduringtheprocess.Finally,allthesurfacesarewitheachotherbytheappliedpressureandtempera-andthus,thesoundsolid-stateweldisproduced.Therefore,mechanismofweldformationinFSWwillbeclearlyknownwhentheroleoftoolisunderstood.Thematerialflowanal-isanimportanttooltounderstandtheroleofFSWtoolonofweldformation.Thereareanumberofexperimentalstudies1115,andwork1618hasbeencarriedouttoanalyzematerialflow,anditisreportedthatthematerialflowiniscomplexanditisnotclearlyunderstood.Ingeneral,thewvisualizationstudieshavebeenconductedbyintroducingaermaterialintheweldline,orbyweldingdissimilarmateri-Afterwelding,themarkermaterialpositionistracedbackbymeans,i.e.,X-rayradiographyortomography11,12differentialetchingprocedure1315,andcomparedwithitsposition.But,ithasbeensaidthattheinsertionofmarkerintheweldlinecanalterthenatureofmaterialflowinweldduetodifferentmaterialflowcharacteristicsofthebasemarkermaterialsandintroductionofadditionalinterfaces.Ontheotherhand,thematerialflowindissimilarmaterialsdifferentflowpropertiescannotbecomparedwithmaterialwinfrictionstirweldsofsimilarmaterials.TheimportantutiontomaterialflowvisualizationisdonebyFratiniet20.Theyincorporatedthematerialflowandanalysiswithevolution.Aninterestingphenomenoninfrictionstirweldsisforma-ofringpattern.ThishasbeenstudiedbyFratinietal.andKrishnan21.Krishnan21explainedtheonionformationusingaclaymodel.Hepointedoutthattheofonionringisageometriceffect.Hestatedthatsemi-ylindricalsheetsofmaterialareextrudedduringeachrotationthetoolandcross-sectionalslicethroughsuchasetofsemilength4.6ofthepinInflothematerialTheotherimportantaspectisdefectformationinfrictionwelds.Kimetal.22andElangovanandBalasubramanianreportedexcessiveflashformation,cavity,tunneldefectandvelikedefects.Andfurthertheyconcludedthatthedefectisduetoinsufficientheatinput,excessiveheatinputabnormalstirring.Zangetal.19reportedthattheporeinafrictionstir-weldedmagnesiumalloyisduetoficientpressureunderneaththeshoulder.But,thereisnoavailableontheroleoftoolgeometryondefectInthisinvestigationasimpleexperimentalmethodispro-toanalyzetheroleoffrictionstirweldingtoolonfrictionweldformationbyanalyzingthematerialflow.Inthisthematerialflowisanalyzedwithouttheinsertionofermaterial.Basedonobservationsmadeintheanalysis,offrictionstirweldformation,defectformationonionringformationareproposed.ExperimentalmethodsThebasematerialusedinthisstudyis7020-T6.Aluminiumy7020isamediumstrengthprecipitationhardenablealloy,whichisusedinaerospaceindustryforstruc-applications.ThenominalchemicalcompositionoftheyisZn4.63wt.%,Mg1.13wt.%,andrestaluminium.basematerialdimensionis300mm75mm4.4mmsquareedges.Thetoolusedinthisstudyis4.2mmlongshapedpinof6mmtopdiameterand4mmbottomwith20mmdiameterflatshoulder.Thefrustumshapedprofileischosenaccordingtotheself-optimizedtoolgeom-suggestedbyPradoandMurr24.Thetoolmaterialis(H13),andishardenedto55HRC.Inthisinvestigation,speed,toolrotationspeedandbackwardtooltiltanglekeptconstantat80mm/min,1400rpm,and2,respectively.FSWtrialsarecarriedoutonakneetypeverticalmillingwithsquarebuttjointconfiguration.Theexperimentisconductedinsuchawaythatthetoolandmaterialinteractioniscontinuouslyincreasedbylinearlytheinterferencebetweentoolshoulderandthebasesurface.ThisisdonebykeepingthebackingplateatantotheweldlineasshowninFig.2.Initiallythe4.2mmtoolpinisplunged3.8mm,andthetoolplungingreachesmmbytheendoftheweld.Inordertoavoidthedamagethebackingplateanaluminiumsupportpieceiskeptbeneathworkpiece.Theideaoftheexperimentisthattheroleoftoolandshoulderonweldformationcanbeanalyzedseparately.ordertoexplaintheeffectoftoolinteractiononthematerialwandweldformationintermsofheatinputandtemperature,axialloadsaremeasuredforthecorrespondingtoolandbaseinteraction.K.Kumar,S.V.Kailas/MaterialsScienceandEngineeringA485(2008)367374369Fig.2.Experimentaldetails.Thebackingplatewaskeptatananglesuchthattheaxialloadcanbelinearlyincreased(from4to10.9kN)bylinearlyincreasingtheinterferencebetweentoolandmaterialbeingwelded.Afterwelding,metallographicsamplesarepreparedfromtheweldcouponatevery20mminterval.Standardmetallographicpracticeisfollowed,anddilutedKellersreagentisusedforetching.3.Resultsanddiscussion3.1.MaterialflowandweldformationFig.3showsthecross-sectionsoftheweldtakenatvarioustoolinterferencelevelswiththebasematerial,withincreasingaxialloads.Itcanbeseenthatthedefectsizereducesasthetoolinterferenceincreases.Itcanalsobenoticedthattheaxialloadincreasesasthetoolinteractionincreases.Aboveanormalloadof7.4kN(Fig.3f),defectshavedisappeared.AsBuffaetal.2reported,therequirementforfrictionstirweldingprocesstoproduceadefect-freeweldisbygeneratingsufficientamountoffrictionalheat,therebygeneratingrequiredtemperatureandhydrostaticpressureintheweldline.AsColegroveandShercliff18explained,theshoulderisthesourceoffrictionalheat,anditpreventsthematerialfromflowingoutoftheweldcavity.Inthepresentsetofexperiments,attheinitialstagesoftheweld-ingthetoolshoulderisnotinfullcontactwiththebasematerial,andhenceaxialloadisinsufficientforheatgeneration.Thefric-tionalheatgeneratedinthisstageisduetotheinteractionoftheshoulderandtheflashmaterial,frictionalheatgeneratedbytheinteractionofthepinwiththebasematerialandheatgeneratedduetotheplasticofthedeformedmaterial.Theprimaryreasonforhavingdefectintheweld,attheinitialstages,wheretheaxialloadislessthan7.4kN,isthelackofshouldercontactwiththebasematerial.Whentheshouldercontactincreaseswiththebasematerialtheaxialloadincreases.Whentheaxialloadisabove7.4kN,thetransferredmaterialfromtheleadingedgeiscon-finedintheweldcavity,andsufficientamountoffrictionheatandhydrostaticpressureisgeneratedtoproduceadefect-freeweld.Theotherobservationisthattheweldcross-sectionissym-metricabouttheweldlineuntiltheaxialloadexceedthe8.1kN(Fig.3af),andabovethisloadtheweldlosesitssymmetry(Fig.3gandh).ItisevidentfromFig.3gandhthatthebaseFig.3.Evolutionofadefect-freeweldasafunctionoftheshoulderinteractionwiththebasematerial.Arrowmarksindicatethepresenceofvoidsintheweld.370K.Kumar,S.V.Kailas/MaterialsScienceandEngineeringA485(2008)367374materiallosesitssymmetrybecausethebasematerialfromtheretreatingsideisdrawnintotheweldnuggetregion.Itcanbenoticedthatthebasematerialmovementawayfromthepincanonlybeinfluencedbytheshoulder.Whenahardandasoftmaterialarerubbedagainsteachother25thesurfaceandsub-surfacematerialflowsinthedirectionofslidingandtheamountofmaterialflowisafunctionofcontactload.Consequently,infrictionstirwelds,whentheaxialloadincreasesaboveacriti-calvaluethesub-surfacematerialflowbecomesintense.Havingthebackwardtooltilt,thecontactpressureinthetrailingedgeofthetoolishigher,andhencethereisbasematerialmovemen