Hot compressive deformation behavior of 7075 Al al

123JournalofMaterialsScienceFullSet-Includes`JournalofMaterialsScienceLetters'ISSN0022-2461Volume47Number3JMaterSci(2012)47:1306-1318DOI10.1007/s10853-011-5904-yHotcompressivedeformationbehaviorof7075AlalloyunderelevatedtemperatureY. C. Lin,Lei-TingLi,Yan-XiangFu&Yu-QiangJiang123YourarticleisprotectedbycopyrightandallrightsareheldexclusivelybySpringerScience+BusinessMedia,LLC.Thise-offprintisforpersonaluseonlyandshallnotbeself-archivedinelectronicrepositories.Ifyouwishtoself-archiveyourwork,pleaseusetheacceptedauthor’sversionforpostingtoyourownwebsiteoryourinstitution’srepository.Youmayfurtherdeposittheacceptedauthor’sversiononafunder’srepositoryatafunder’srequest,provideditisnotmadepubliclyavailableuntil12monthsafterpublication.Hotcompressivedeformationbehaviorof7075AlalloyunderelevatedtemperatureY.C.Lin•Lei-TingLi•Yan-XiangFu•Yu-QiangJiangReceived:29May2011/Accepted:25August2011/Publishedonline:13September2011SpringerScience+BusinessMedia,LLC2011AbstractThehotcompressiontestswereconductedwithwidestrainratesandformingtemperaturerangestostudythehigh-temperaturedeformationbehaviorof7075Alalloy.Thematerialflowbehaviorandmicrostructuralevolutionduringhot-formingprocessarediscussed.Basedonthemeasuredstress–straindata,anewconstitutivemodelisproposed,consideringthecoupledeffectsofstrain,strainrate,andformingtemperatureonthematerialflowbehaviorof7075Alalloy.Intheproposedmodel,thematerialconstantsarepresentedasfunctionsofformingtemperature.Theproposedconstitutivemodelgivesgoodcorrelationswiththeexperimentalresults,whichconfirmsthattheproposedmodelcangiveanaccurateandpreciseestimateofflowstressfor7075Alalloy.IntroductionAluminumalloysareselectedfortheiroptimalcombi-nationofphysicalandmechanicalproperties,suchasalloystrength,ductility,fatigueresistance,fracturetoughness,andcorrosionresistance.7075Alalloyisextensivelyusedforstructuralapplicationsduetoitshighstrength/densityratioandreasonablehighfracturetoughness[1–4].Generally,thecast7075Alalloyswillbesubjecttovarioushot-formingprocesses,suchasrolling,forging,extrusion,andheattreatments.Themechanicalpropertiesarecloselyrelatedtothemicro-structuresofthesealloys,whicharegreatlyinfluencedbythermomechanicalprocessing.Meanwhile,materialflowbehaviorduringhotformationprocessisoftencomplex.Thehardeningandsofteningmechanismsarebothsig-nificantlyaffectedbythethermo-mechanicalparameters,suchasformingtemperature,degreeofdeformation,andstrainrate.TheunderstandingofAlalloysbehaviorathotdeformationconditionisofgreatimportancefordesignersofmetalformingprocesses(hotrolling,forging,andextrusion)becauseofitseffectiveroleonmetalflowpatternaswellasthekineticsofmetallurgicaltransfor-mation[5–10].Theconstitutiverelationisoftenusedtodescribetheplasticflowpropertiesofthemetalsandalloysinaformthatcanbeusedincomputercodetomodelthedynamicresponseofmechanicalpartmembersundertheprevailingloadingconditions.Therefore,anumberofresearchgroupshaveattemptedtodevelopconstitutiveequationsofmaterialsfromtheexperimen-tallymeasureddatatodescribethehotdeformationbehavior[11–25].LinandChen[11]presentedacriticalreviewonsomeexperimentalresultsandconstitutivedescriptionsformetalsandalloysinhotworkinginrecentyears,andtheconstitutivemodelsaredividedintothreecategories,includingthephenomenological,physical-based,andartificialneuralnetworkmodels,tointroducetheirdevelopments,predictioncapabilities,andapplica-tionscopes,respectively.Linetal.[12]proposedaY.C.Lin(&)L.-T.LiY.-Q.JiangSchoolofMechanicalandElectricalEngineering,CentralSouthUniversity,Changsha410083,Chinae-mail:[e-mail];[e-mail]L.-T.LiY.-Q.JiangStateKeyLaboratoryofHighPerformanceComplexManufacturing,Changsha410083,ChinaY.-X.FuSchoolofMechanicalEngineering,XiangtanUniversity,Xiangtan411105,China123JMaterSci(2012)47:1306–1318DOI10.1007/s10853-011-5904-yAuthor'spersonalcopyrevisedArrheniusconstitutivemodeltodescribetheeffectsofstrainonmaterialconstantsontheflowbehaviorof42CrMosteeloverawiderangeoftemper-atureandstrainrate.Also,someotherinvestigatorsestablishedtheconstitutiveequationsforvariousmetalsandalloys,consideringthecompensationofthestrain[13–19].Castellanosetal.[20–22]proposedanewcon-stitutivestrain-dependentGarofaloequationtodescribethehigh-temperatureprocessingofAZ31magnesiumalloy,anddiscussedtheeffectsofadiabaticheatingontheGarofaloequationparametersofsomesteels.Also,Phanirajetal.[23]performedconstitutiveanalysisfol-lowingtheGarofalosine–hyperbolicequationonthetruestress–straindataobtainedfromisothermalhotcompres-siontestsonmodified9Cr–1Mo(P91)steeloverawiderangeoftemperatureandstrainrate.Althoughgreatprogressesinthedevelopmentofcon-stitutivemodelshavebeenmade,thephysicalmodelsarestillnotadvancedenoughtoaccountforthewholecom-plexityofthedynamicresponseof7075Alalloys.Inthisstudy,thehigh-temperaturedeformationbehaviorandmicrostructuralevolutionof7075Alalloyareinvestigated.Consideringthecoupledeffectsofstrain,strainrate,andformingtemperature,anewconstitutivemodelisproposedtopredicttheflowstressfor7075Alalloy.ExperimentsAcommercial7075Al