关于焊接方面的英文文献

关于焊接方面的英文文献JournalofMaterialsProcessingTechnology180(2006)216–220Studiesonsofteningofheat-affectedzoneofpulsed-currentGMAweldedAl–Zn–MgalloyGaofengFu∗,FuquanTian,HongWangSchoolofMaterialsandMetallurgy,NortheasternUniversity,Shenyang110004,ChinaReceived15December2005;receivedinrevisedform9June2006;accepted12June2006AbstractStudiesonthesofteningbehaviorofthe7005alloybymeansofrealweldingexperimentsandheat-affectedzone(HAZ)simulationhavebeenconducted.SofteningintheHAZisfoundtooccuraboveapeaktemperatureofabout200◦C.Itwasfoundthattheheat-affectedzoneofthealloyscanbedividedintotwosub-zonesaccordingtotheirdifferentmechanismofsoftening:thedissolutionzoneandtheoverageingzone.Thedissolutionzoneischaracterisedbydissolutionofprecipitatesandcoversthepeaktemperaturerangeabove380◦C.Theoverageingzoneischaracterisedbygrowthofprecipitatesandcoversthepeaktemperaturerangebetween230and380◦C.Thehardnessintheheat-affectedzonecanberecoveredbypost-weldheattreatment,especiallyinthedissolutionzone.Artificialageingismoreeffectivethannaturalageingconsideringtherecoveryofthehardness.©2006ElsevierB.V.Allrightsreserved.Keywords:Aluminumalloys;Heat-affectedzone;Softening;Welding;Thermalsimulation1.IntroductionTheAl–Zn–Mgalloyhaswideacceptanceinfabricationoflightweightstructuresrequiringahighstrength-to-weightratio,suchasstoragetanksofspacerockets,transportablebridgegird-ersandrailwaytransportsystems[1–3].∗Correspondingauthor.Tel.:+862483681325;fax:+862423906316.AlthoughthegeneraltransformationbehaviourofAl–Zn–Mgalloysisknown,detailedknowledgeaboutHAZsofteninginsomeindividualalloysislacking.ThepurposeofthispaperistoobtainfundamentalinsightintheHAZsofteningcharacteristicsofthe7005alloyduringpulsed-currentGMAwelding,andtofindouthowthesofteningisaffectedbyheatinputandpost-weldheattreatment.2.Materialsandexperimentalprocedure2.1.Materials0924-0136/$–seefrontmatter©2006ElsevierB.V.Allrightsreserved.doi:10.1016/j.jmatprotec.2006.06.008。G.Fuetal./JournalofMaterialsProcessingTechnology180(2006)216–220217Table1WeldingparametersLowheatinputconditionsHighheatinputconditionsArcvoltage(V)2525Arccurrent(A)200200Travelspeed(cm/min)6030ShieldinggasArgonArgonGasflowrate(l/min)1414Fillerwire,diameter(mm)ER5356,1.2ER5356,1.2PolarityDCEPDCEPProcessefficiency(%)6565Heatinput(J/mm)5001000alsocontaining0.2Cr,0.02Ti,Fe<0.4,Si<0.35andCu<0.1.Thespecimensweremachinedfromtheas-extruded7005bars.2.2.HAZsimulationHAZsimulationwascarriedoutbyimposingthermalcyclesonaseriesofsmallspecimens,havingdimensions10mm×10mm×60mm.Thespecimensweremachinedfromtheplatematerial,thelongestdimensionparalleltotherollingdirectionoftheplate.Twosetsofweldingconditionswereselectedforsimulation,correspondingtoheatinputsof500and1000J/mm,respectively(Table1).TheHAZsinthecaseofbothheatinputsweresimulatedbythermalcycleswithpeaktemperaturesbetween150and600◦C,whichforthegivenheatinputrepresentspecificlocationsintheHAZ.ThethermalcyclesusedintheHAZsimulationwerecalculatedwiththemodifiedRosenthalmodelfortwo-dimensionalheatflow.ThepropertiesoftheHAZareusuallyexpressedeitherasafunctionofpeaktemperatureorasafunctionofdistancefromthefusionboundary.Inviewofthis,itisconvenienttoknowtherelationbetweenthepeaktemperatureandthedistancefromthefusionboundary.Thisrelationwasdeterminedforthetwoheatinputsusedinthiswork(500and1000J/mm).TheresultsareshowninFig.1。.Fig.1.Therelationbetweenpeaktemperatureandthedistancefromthefusionboundaryfortwoheatinputs(500and1000J/mm).2.3.WeldingexperimentsInordertoexaminetheinfluenceofheattreatmentonthemicrostructureandpropertiesofthematerials,thesimulatedandweldedspecimensweresubjectedtooneofthefollowingheattreatments:。1.naturalageing(4monthsatroomtemperature);2.artificialageing(24hat120◦C);3.stepageing(8hat100◦C+24hat150◦C).2.5.ExaminationofhardnessandmicrostructureHardnessmeasurementsofboththesimulatedandweldedspecimenswerecarriedoutusingaVickershardnessmachine(5kgload).Tostudythemicrostructureofthesimulatedandweldedspecimenscross-sectionsweremade,whichweresubsequentlygroundandetchedusingKellersolution.Themicrostructurewasprimarilyexaminedbymeansofopticalmicroscopy(NeophotII).Additionally,transmissionelectronmicroscopy(TEM)wascarriedoutusingaPhilipsEM400.ThethinfoilsrequiredfortheTEMexaminationwerepreparedbyjetpolishing.3.Resultsanddiscussion3.1.SofteningoftheHAZ。Inordertodeterminetheeffectofweldingonthehardnessofthe7005alloy,specimensweresimulatedandexaminedfollow-ingtheproceduredescribedintheprevioussection.InFig.2thehardnessofthealloysimmediatelyaftersimulationisplottedasafunctionofthepeaktemperatureforthesituationcorrespond-ingwithaheatinputof500J/mm.Thefigureshowsthatsofteningoccurswhenthepeaktem-peratureishigherthanabout200◦C,whichisequivalentwithsofteninginazonehavingawidthofabout12mmadjacenttothefusionboundary.Asalreadymentionedabove,softeningoftheHAZinheat-treatablealuminiumalloysisdirectlyrelatedtomodificationofprecipitates.3.2.ModificationofprecipitatesTobeabletoobtainadditionalinformationaboutthepre-cipitationbehaviourofthealloysduetowelding,transmission。218G.Fuetal./JournalofMaterialsProcessingTechnology180(2006)216–220Fig.2.Hardnessasafunctionofpeaktemperatureofsimulatedspecimensdirectlyaftersimulation(heatinput500J/mm).electronmicroscopy(TEM)wascarriedoutonbothas-receivedandsimulatedspecimens.Fig.3showsTEMmicrographsof7005specimenssimulatedatdifferentpeaktemperatures.InFig.3(a)themicrostructureofthenon-simulatedparentmetalisshowninwhichsmallprecipitatesarevisible.Duringsim-ulationuptoapeaktemperatureof200◦Ctheprecipitatesremainvirtuallyunchanged(Fig.3(b)).However,simulationatapeaktemperatureof300◦C,leadstodissolutionandgrowthofprecipitates(Fig.3(c)).Whenthepeaktemperatureexceeds400◦C,allprecipitatesaredissolved(Fig.3(d)).OnthebasisoftheseobservationsitmaybeconcludedthatthelossofhardnessintheHAZisduetodissolutionand/orgrowthof。precipitates.Fig.4.Hardnessasafunctionofpeaktemperatureofsimulatedspecimensof7005alloyfortwoweldingconditions.Aftersimulation,thespecimensweretreatedbyartificialageing.Toseparatethesofteningeffectduetodissolutionfromthatduetoth