铝合金时效处理

IntJAdvManufTechnol(2008)37:294–301DOI10.1007/s00170-007-0970-7

ORIGINALARTICLE

EffectofpostweldagingtreatmentontensilepropertiesofelectronbeamweldedAA2219aluminumalloy

S.Malarvizhi&K.Raghukandan&N.Viswanathan

Received:21August2006/Accepted:29January2007/Publishedonline:24February2007#Springer-VerlagLondonLimited2007

AbstractAluminumalloy2219(Al-6.5%Cu)isafavouriteagehardenablealloyforaerospaceapplicationsbecauseofitsexcellentweldingcharacteristics.ThoughAA2219hasgotanedgeoverits6000and7000seriescounterpartsintermsofweldability,italsosuffersfrompoorjointstrengthwhenwelded.Inthisinvestigationanattempthasbeenmadetoimprovetheweldedjointstrengththroughpostweldagingtreatment.Thispaperpresentstheeffectofpost-weldagingtreatmentontensilepropertiesofelectronbeamweldedAA2219aluminumalloy.Squarebuttjointswerefabricatedusinganelectronbeamwelding(EBW)machineof100kVcapacity.Thejointsweregivenpost-weldartificialagingtreatment.Tensiletestswerecarriedoutusing100kN,electro-mechanicalcontrolleduniversaltestingmachine.Itisfoundthatthepost-weldagingtreatmentisbeneficialforimprovingweldmetalhardnessandtensileproperties.ThisismainlyduetotheuniformdistributionofCuAl2precipitatesintheweldmetalregioninpost-weldagedjointscomparedtoasweldedjointsasevidentfromweldmetalmicrostructure.

KeywordsAA2219alloy.Electronbeamwelding.Artificialaging.Tensileproperties

1Introduction

Aluminumalloy2219(Al-6.5%Cu)isafavouriteagehardenablealloyforaerospaceapplications,becauseofitsexcellentweldabilitycharacteristics.Theotheragehardenablealloysbelongingto6000(Al-Si-Mg)and7000(Al-Zn-Mg)seriessufferfromsolidificationcrackingandhavetobeweldedusingnon-heattreatablefillers.AA2219isbasicallyAl-Cu-Mnternaryalloy.AA2219ismostwidelyusedmaterialfortheconstructionofliquidcryogenicrocketfueltanksandhasauniquecombinationofpropertiessuchasgoodweldability,highstrengthtoweightratioandsuperiorcryogenicproperties[1].

ThepreferredweldingprocessesforAA2219aluminumalloyarefrequentlygasmetalarcwelding(GMAW)andgastungstenarcwelding(GTAW),duetotheircompara-tivelyeasierapplicabilityandbettereconomy.However,plasmaarcwelding(PAW)withapositivepolarityelectrodeandhighweldingcurrentallowsaluminumcomponentstobejoinedeconomicallywithanexcellentweldquality.Theincreasingdemandforusingcompara-tivelythickersectionsofaluminumalloysinseveralfields,suchaspressurevessels,structuralcolumnsandtransportsystemsnecessitatesmultipassweldingforjoiningofthosesections.Inmultipasswelding,theweldcharacteristics,andconsequentlyitsmechanicalproperties,differfromthoseobservedinthecaseofsinglepasswelds[2].

IncomparisonwithGTAWandGMAWarcs,electronbeamischaracterizedbyhigherpowerdensityandthuspermitssinglepassweldingofsquarebuttjointswiththicknessuptoapproximately8mminflatpositionatweldingspeedsuptomorethan1m/min.ItisknownthattheelectronbeamweldsofmostoftheweldablematerialsincludingaluminumalloysexhibitsuperiormechanicalpropertiescomparedtotheweldsmadeusingGTAW.

S.Malarvizhi(*)K.Raghukandan

DepartmentofManufacturingEngineering,AnnamalaiUniversity,

AnnamalaiNagar608002TamilNadu,Indiae-mail:jeejoo@http://www.77cn.com.cn

N.Viswanathan

DefenceResearch&DevelopmentLaboratory,Kanchanbagh(P.O),

Hyderabad560054AndhraPradesh,India

IntJAdvManufTechnol(2008)37:294–301ComparisonofmechanicalpropertiesreportedinliteratureshowsthatthedifferenceintensileandproofstrengthvaluesbetweenEBweldsandGTAorVariablePolarityPlasmaArcweldswasabout100MPa,particularlyincaseofthickersections[3].

Comparedto6000and7000seriesalloysAA2219alloyiseasilyweldable,butitalsosuffersfrompoorasweldedjointstrength.Thejointstrengthisonlyabout40%whencomparedtothebasemetalstrengthinT87condition.Thisistruebothinautogenousweldsaswellasthoseweldedwiththematchingfiller2319,whichcontainsslightlyhighercontentsofTiandZr.Thelossofstrengthisduetothemeltingandquickresolidification,whichrendersallthestrengtheningprecipitatestodissolveandthematerialisasgoodasacastmaterialwithsolutesegregationandlargecolumnargrains[4].

Hence,inthisinvestigationanattempthasbeenmadetoimprovethetensilepropertiesofelectronbeamweldedAA2219aluminumalloybymeansofsimplepost-weldartificialagingtreatment.Theeffectofpost-weldartificialagingtreatmentontensilepropertiesofelectronbeamweldedAA2219aluminumalloyisreported.

2Experimentalwork

Thebasemetal(BM)usedinthisinvestigationwasrolledplatesofAA2219aluminumalloy,whichwerecutintotherequiredsizes(300×150×12mm)bypowerhacksawcuttingandgrinding.ThechemicalcompositionandmechanicalpropertiesofbasemetalarepresentedinTable1and2.Squarebuttjointconfigurationwaspreparedtofabricateelectronbeamweldedjoints.Thejointswerefabricatedusinganelectronbeamwelding(EBW)machine(Techmeta,France)of8KWcapacity.TheweldingconditionsandprocessparameterspresentedinTable3wereusedtofabricatethejointsbyEBWprocess.

Inmostoftheheattreatablealloys,partoftheHAZisdegradedtosuchanextentthatmechanicalpropertiescanbeimprovedonlybyapplyingafullheattreatmentafterwelding(solutiontreatment+aging).WithAl-Cualloys,however,jointpropertiesareimprovedbyasimpleprecipitation(aging)treatment,afterwelding,thewholeoftheweldzonehardening[5].Tostudytheinfluenceofpost-weldagingtreatmentontensileproperties,theweldedjointsweredividedintotwogroupsviz.,(i)aswelded(AW)jointsand(ii)artificiallyaged(AA)joints.

Table1Chemicalcomposition(wt%)ofbasemetalCuMnFeZrVSiTiZnAl6.33

0.34

0.13

0.12

0.07

0.06

0.04

0.02

Bal

295

Table2MechanicalpropertiesofbasemetalYieldUltimateElongationReductionVickersstrengthtensile(%)

incross-hardness(MPa)

strengthsectional(0.05kg),(MPa)area(%)VHN392475

15

10

140

Foraswelded(AW)joints,nopost-weldheattreatmentwasgivenandthemechanicalandmetallurgicalpropertieswereevaluatedimmediately(withinaweekperiod)afterwelding.Artificialaging(AA)treatmentwascarriedoutat175°Cforasoakingperiodof12hours.Jointswereplacedintotheinduct …… 此处隐藏：18788字，全部文档内容请下载后查看。喜欢就下载吧 ……